STEAM  WELLS  AND  OTHER  THERMAL 
ACTIVITY  AT  "THE  GEYSERS" 

CALIFORNIA 

By 

E.  T.  ALLEN  and  ARTHUR  L.  DAY 


Published  by  the  Carnegie  Institution  of  Washington 

1927 


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Carnegie  Institution  of  Washington,  Publication  No.  378 


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FIG.  1— CONTOUR  MAP  OF  A  PORTION  OF  “THE  GEYSERS"  IN  SONOMA  COUNTY,  CALIFORNIA, 


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CARNEGIE  INSTITUTION  OF  WASHINGTON 


Publication  No.  378 


1927 


PRESS  OF 

W.  F.  ROBERTS  COMPANY 
WASHINGTON.  D.  C. 


STEAM  WELLS  AND  OTHER  THERMAL 
ACTIVITY  AT  “THE  GEYSERS” 

CALIFORNIA 


■J  By 

E.  T.  ALLEN  and  ARTHUR  L.  DAY 


Published  by  the  Carnegie  Institution  of  Washington 

1927 


CONTENTS 


/ 


Page 


Introductory .  9 

“ The  Geysers” .  11 

Springs  and  Fumaroles .  14 

Temperatures  at  The  Geysers .  23 

Surface  Drainage  and  Its  Effect  on  the 

Springs .  26 

Discharge  of  the  Hot  Springs  on  Geyser 

Creek .  29 

The  Spring  Waters .  31 

Salts .  38 

Sediments .  45 

The  Steam-Wells .  50 

Pressure,  Temperature,  and  Output 

of  the  Steam- Wells .  55 

Characteristics  of  Subterranean  Steam 

in  Other  Localities .  63 

Non-condensable  Gases  in  the  Steam  .  .  64 

Analysis  of  the  Non-condensable  Gases  68 

Composition  of  the  Gases .  70 

Soluble  Gases .  72 

Hydrogen  Sulphide .  72 

Ammonia .  74 

Boric  Acid .  76 

Summary  of  Gas  Analyses .  76 


Page 

Comparison  of  Amounts  of  Sulphur  and 
Ammonia  in  Gases  and 


Springs .  77 

Processes  of  Spring  Formation .  77 

Temperature  Gradient .  81 

Cause  of  the  Heat .  86 

Origin  of  Steam  at  The  Geysers .  89 

Superheated  Condition  of  the  Steam ...  90 

Transmission  of  Steam  from  its  Source 

to  the  Surface .  91 

Duration  of  the  Wells .  92 

Thermal  Activity  at  other  Points 

Aligned  with  The  Geysers ....  93 

Sulphur  Banks .  94 

Little  Geysers .  95 

Calistoga .  98 

Comparison  of  The  Geysers  Canyon, 
California,  with  the  Fumarole 

Fields  of  Tuscany .  100 

Steam  Wells .  101 

Steam  Output .  102 

Gases .  102 

Summary . 104 

Acknowledgment .  106 


5 


ILLUSTRATIONS 


FIG.  PAGE 

1 —  Contour  Map  of  a  Portion  of  “The 

Geysers”  in  Sonoma  County 
California . Opposite  Title  Page 

2 —  Sulphur  Creek  Canyon  Looking 

East .  10 

3—  Looking  up  Geyser  Creek  in  early 

morning  when  huge  steam  clouds 
obscure  upper  slopes .  12 

4 —  Looking  north  in  Geyser  Creek 

canyon  at  noon  when  free  from 
steam .  13 

5 —  Chert  exposure  (left)  on  west  bank 

of  Geyser  Creek .  14 

6 —  The  Smokestack  at  noon  when 

least  steam  is  visible .  15 

7 —  The  Safety  Valve  seen  at  midday .  .  16 

8 —  The  Steamboat  Fumarole  in  morn¬ 

ing  hours .  17 

9 —  At  right  and  left  in  foreground  are 

two  bubbling  springs  known  as 
the  Witches’  Cauldrons.  Photo 
taken  when  inundated  by  creek. .  19 

10 — Looking  down  on  Witches’  Caul¬ 
drons  from  above.  Note  effect 


of  inky  precipitate .  20 

11 —  Acid  springs  in  overhanging  east 

bank  of  Geyser  Creek .  21 

12 —  “  Washtub  ”,  Geyser  Canyon .  22 

13 —  One  of  chain  of  springs  along  Gey¬ 

ser  Creek .  23 

14 —  Geyser  Creek  canyon  looking  north 

at  midday.  Devil’s  Pulpit 
slightly  to  left  of  center .  28 

15 —  Salt  incrustations  beside  Steam¬ 

boat  F  umarole .  39 

16 —  Magnesium  sulphate  occurring  in 

cavities  of  serpentine .  40 


17 —  Salts  encrusting  wall  rock  of 

Devil’s  Kitchen  where  acid  am¬ 
monium  sulphates  were  found ...  41 

18 —  Slope  above  Devil’s  Arm  Chair. 

One  of  localities  for  acid  am¬ 


monium  sulphates .  43 

19 — Drilling  first  well.  The  Geysers, 

1922 .  50 


FIG.  PAGE 

20—  A  plank  across  mouth  of  casing, 

weighted  with  drill  rod  weigh¬ 
ing  about  a  ton,  fails  to  “hold 
down”  steam,  1922 .  51 

21—  Drilling  second  well  with  steam 

power  from  first.  Photo  ob¬ 
tained  from  J.  D.  Grant .  52 

22 —  Wells  No.  1  and  No.  2  discharging 

into  atmosphere,  1924.  Ex¬ 
cellent  view  of  Smokestack  Fu¬ 
marole  right .  53 

23 —  Wells  open.  No.  1  and  No.  2  left, 

No.  4  center,  No.  5  right  and 
No.  6  partially  closed  down  be¬ 
tween  No.  4  and  No.  5.  1925. . .  55 

24 —  Wells  Nos.  4,  5,  6  and  7  discharg¬ 

ing.  1925.  Photo  by  Kidd. ...  56 

25 —  Well  No.  6.  Steamboat  Fumarole 

in  foreground .  57 

26 —  Well  No.  6  just  completed  and  shut 

off.  1925 .  58 

27 —  Safety  Valve  in  1925  after  boring 

Wells  No.  4,  No.  5  and  No.  6 .  .  .  .  59 

28—  — Field  equipment  for  determining 

gases  accompanying  steam  at 
Well  No.  2.  1925 .  65 

29 —  Sketch  of  apparatus  for  deter¬ 

mining  ratio  of  gases  to  steam.. . .  66 

30 —  Well  No.  3  as  it  appeared  in  1925. 

Casing  is  coated  with  opal 

formed  by  evaporation  of  small 
amount  of  water  constantly 

thrown  out  with  steam .  83 

31 —  Spring  at  The  Little  Geysers, 

southwest  of  cabin.  (Gas  sam¬ 

ple  No.  4,  table  9,  was  collected 
from  this  spring.) .  96 

32—  — One  of  small  hot  springs  at  The 

Little  Geysers,  Central  Plateau. 

(Gas  sample  No.  3  was  collected 


from  this  spring.) .  97 

33 — Artificial  geysers  at  Calistoga,  Cal- 
fornia,  developed  unexpectedly 
by  drilling.  Photo  by  J.  D. 
Grant .  99 


34 — The  Geysers,  early  morning.  1925  105 


STEAM  WELLS  AND  OTHER  THERMAL 
ACTIVITY  AT  “THE  GEYSERS” 

CALIFORNIA 


By  E.  T.  Allen  and  Arthur  L.  Day 


STEAM  WELLS  AND  OTHER  THERMAL 
ACTIVITY  AT  “THE  GEYSERS,”'  CALIFORNIA. 


INTRODUCTORY 

The  St.  Helena  or  Mayacmas  Range  is  one  of  the  Coast  Ranges  of 
California.  Rising  near  Sonoma  35  miles  north  of  San  Francisco  it 
extends  northwesterly,  parallel  to  the  shore  line  at  a  distance  of 
about  30  miles  and  forms  a  part  of  the  boundary  line  between  Sonoma 
County  on  the  west  and  Napa  and  Lake  Counties  on  the  east.  The 
principal  chain  is  close  to  50  miles  in  length  and  its  highest  peaks 
reach  an  altitude  of  4,500  feet.  A  tributary  ridge  branching  off  at 
Mount  St.  Helena  runs  in  a  direction  somewhat  more  easterly,  almost 
as  far  south  as  the  main  range. 

The  slopes  of  these  mountains  are  covered  with  sediments  and 
metamorphics — sandstones  and  shales,  cherts,  schists  and  serpentines 
which  are  assigned  to  the  Franciscan  formation.  The  backbone  of 
the  range,  however,  is  doubtless  volcanic,  for  lavas,  chiefly  andesite, 
are  exposed  on  the  summits  of  Mount  Cobb,  Mount  St.  Helena  and 
other  high  peaks,  and  there  are  limited  areas  of  lavas,  tuffs  and 
obsidian  in  other  places.2 

Hot  springs  are  numerous  on  both  sides  of  the  range,  but  the 
western  side,  both  on  account  of  its  higher  temperatures  and  greater 
chemical  activity  as  well  as  its  relation  to  recent  industrial  develop¬ 
ment,  is  scientifically  the  more  interesting,  and  to  it,  therefore,  this 
investigation  has  been  exclusively  devoted. 

An  important  relation  between  the  hot  springs  and  many  quick¬ 
silver  mines  of  the  western  side  of  the  range  and  one  which  seems  to 
have  been  entirely  unnoticed  by  others,  has  been  pointed  out  to  the 
authors  by  H.  W.  Gould,  metallurgist  and  quicksilver  producer  of 
San  Francisco,  whose  activities  have  brought  to  him  an  intimate 
knowledge  of  the  geological  features  of  this  district.  Mr.  Gould 
shows,  by  the  map,3  the  almost  rectilinear  alignment  of:  The  Aetna, 
Corona,  Oathill,  Mirabel,  Great  Western,  Helen  and  Socrates  Quick¬ 
silver  Mines,  all  of  which  are  associated — generally  closely  associated 
— with  warm,  hot  or  sulphur  springs;  the  Little  Geysers  and  The 
Geysers,  hot-spring  groups  about  5  miles  apart  with  at  least  three 
lesser  hot-spring  areas  lying  between  them;  hot  springs  at  intervals 

1  Near  Cloverdale,  Sonoma  County. 

2  Map  of  the  State  of  California,  Geology  by  James  Perrin  Smith.  State  Mining  Bureau, 
1916.  Quicksilver  resources  of  California,  Bull.  78  of  the  California  State  Mining  Bureau  1913, 
by  Walter  W.  Bradley  (map  opposite  page  32). 

3  W.  W.  Bradley  referred  to  above.  Not  all  the  localities  mentioned  in  the  text  are  shown 
on  any  map. 


9 


Fig.  2 — Sulphur  Creek  Canyon  looking  east. 


11 


for  a  mile  west  of  The  Geysers;  the  Sulphur  Banks,  an  active 
fumarole  area  and,  finally,  the  Cloverdale  Quicksilver  Mine  which  is 
associated  with  declining  fumarolic  activity.  The  line  connecting  all 
these  points  is  about  25  miles  in  length,  virtually  straight  throughout 
and  roughly  parallel  with  the  mountain  range  with  which  the  original 
volcanic  activity  is  associated.  A  similar  relation  between  hot  springs, 
fumaroles  and  volcanoes  has  been  repeatedly  observed  in  other  places 
where  fault  lines  have  been  traced,  and  it  is  not  improbable  that 
careful  observation  may  adduce  further  evidence  of  a  fault  in  this 
locality.  All  geologists  agree  that  these  faults  must  be  vitally  con¬ 
nected  with  the  cause  of  hot  springs;  their  real  significance  deserves 
close  attention  and  will  be  discussed  later  on. 


“THE  GEYSERS” 

From  The  Little  Geysers  westward  the  hypothetical  fault  line  just 
referred  to  practically  follows  Sulphur  Creek,  the  bed  of  which  is  a 
narrow  canyon  forming  the  southern  boundary  of  the  St.  Helena 
Range.  The  most  active  point  on  this  line  is  “The  Geysers,’1  an  old 
health  resort  18  miles  east  of  Cloverdale  and  25  miles  north  of  Healds- 
burg,  with  both  of  which  it  is  connected  by  stage  road.  The  resort 
consists  of  an  old  hotel,  the  earliest  wing  of  which  is  said  to  date  from 
1852,  a  group  of  cottages  and  a  modern  bath-house.  The  buildings 
are  located  on  the  south1  bank  of  Sulphur  Creek.  The  hot  ground  is 
on  the  other  side  (fig.  2).  Beginning  in  the  bed  of  the  creek,  where 
several  hot  springs  occur,  it  extends  east  and  west  for  an  extreme  dis¬ 
tance  of  400  yards  and  stretches  up  the  steep  slope  of  the  mountain 
to  distances  varying  from  200  to  500  yards.  The  ground  is  dotted  at 
intervals  with  small  hot  springs  and  fumaroles  and  marked  with  thin 
salt  patches  in  dry  weather.  The  name  “Geysers11  is  a  misnomer,  as 
no  geysers  occur  here. 

The  bounds  of  the  hot  ground  are  pretty  sharply  defined;  on  the 
south  by  Sulphur  Creek,  on  the  north  and  east  by  woods,  while  the 
western  limit  is  marked  by  a  steep  ridge  forming  the  western  bank  of 
a  little  tributary  of  Sulphur  Creek  known  as  Geyser  Creek  (figs.  3 
and  4),  up  the  almost  percipitous  bank  of  which  activity  continues 
for  50  or  100  feet  in  the  upper  half  of  the  canyon.  The  total  area  is 
thus  about  35  acres.  It  is  divided  into  two  unequal  parts  by  a  ravine 
which,  beginning  near  the  northern  border  at  a  point  about  500  feet 
east  of  Geyser  Creek  canyon,  drops  rapidly  to  a  depth  of  about  40 
feet  and  runs  southwesterly  for  a  few  hundred  yards,  where  it  opens 
into  Geyser  Creek  canyon.  Along  the  sides  and  to  the  south  of  the 
ravine  close  to  Sulphur  Creek,  as  well  as  along  the  lower  reaches  of 
Geyser  Creek  canyon,  there  is  a  growth  of  live-oak,  pepperwood  and 

1  The  trend  of  the  range  for  several  miles  in  this  vicinity  is  more  nearly  east  and  west  than  is 
the  general  trend. 


12 


manzanita;  elsewhere  the  ground  is  bare  or  sparsely  covered  with 
grass  or  weeds.  Seen  at  a  little  distance  in  warm,  dry  weather  when 
no  steam  is  visible,  this  rather  diminutive  area  appears  not  unlike  any 
other  of  the  numerous  open  spaces  which  constantly  recur  among  the 
dark-green  oaks  on  these  steep  declivities  and  which,  covered  with  a 
carpet  of  short,  dry  grass,  golden  in  the  summer  sun,  are  so  charac¬ 
teristic  of  the  Coast  Mountains. 


Fig.  3 — Looking  up  Geyser  Creek  in  early  morning  when  huge  steam  clouds  obscure 

upper  slopes. 


Like  most  of  the  St.  Helena  Range  this  area  is  covered  with  sedi¬ 
ments  and  metamorphic  rocks.  Along  the  eastern  border  sandstones 
outcrop  all  the  way  to  the  top  of  the  mountain  ridge,  and  drilling  has 
proved  that  sandstones  and  in  some  places  shales  and  cherts  underlie 
the  hot  ground  at  depths  sometimes  less  than  100  feet.  The  same 
rocks  are  also  plentifully  exposed  along  the  banks  of  Sulphur  Creek 
not  far  down  stream  and  along  the  highways  of  the  vicinity.  Chert 


13 


is  exposed  on  the  banks  of  Sulphur  Creek  and  at  one  point  on  Geyser 
Creek  (fig.  5).  High  above  the  hot  area  and  within  half  a  mile  of  it, 
stands  a  great  ledge  of  mica  schist,  while  serpentine  and  serpentine 
conglomerates,  so  common  in  the  Coast  Range,  occur  in  several  places. 
The  conglomerates  form  low  cliffs  along  the  two  creeks  where  they 
are  in  process  of  decomposition,  and  a  prominent  outcrop  of  the  fresh 


Fig.  4 — Looking  north  in  Geyser  Creek  canyon  at  noon 
when  free  from  steam. 


serpentine  is  found  in  about  the  center  of  the  area  along  the  trail  to 
Steamboat  Fumarole.  No  igneous  rock  has  been  found  at  the  surface, 
but  that  an  intrusion  reaches  up  to  a  level  not  far  below  it  is  one  of 


14 


the  interesting  facts  which  has  been  disclosed  by  drilling.  A  core 
taken  from  Well  No.  5  at  a  depth  of  about  230  feet  was  submitted  to 
F.  E.  Wright  for  examination  and  found  to  be  gabbro. 


Fig.  5 — Chert  exposure  (left)  on  west  bank  of  Geyser  Creek. 


SPRINGS  AND  FUMAROLES 

Well-marked  fumaroles  are  found  at  The  Geysers  in  only  a  few 
places.  The  Smokestack  (fig.  6;  see  map,  fig.  1),  which  opens  at  a 
point  40  feet  up  on  the  western  bank  of  Geyser  Creek  near  the  Devil’s 
Pulpit,  pours  out  the  greatest  volume  of  steam.  It  issues  from  a 
little  flat  on  the  otherwise  precipitous  slope  and  on  account  of  the 
slippery  mud  is  accessible  only  from  above.  A  climb  to  it  in  July  1924 
revealed  a  little  basin,  the  dried  mud  of  which  indicated  the  presence 
of  water  in  wet  weather.  Much,  if  not  most  of  the  rain  on  this  steep 
slope  doubtless  runs  off,  but  the  ground  to  the  west  rises  several 


15 


hundred  feet  higher  and  there  is,  therefore,  no  reason  to  believe  that 
a  hot  spring  can  not  exist  there  in  the  wet  season. 

About  125  feet  down  stream  on  the  opposite  bank  of  Geyser  Creek 
and  perhaps  30  feet  above  it,  the  Safety  Valve  (fig.  7)  emits  several 
jets  of  steam  from  the  muddy  bank;  but  the  most  distinctive  fumarole 
in  the  district  and  the  one  best  known  to  tourists  is  the  Steamboat 
(fig.  8),  the  strong  vertical  and  constantly  puffing  steam  jet  of 
which  gives  to  it  its  name.  Short  iron  pipes  1.5  inches  in  diameter 


Fig.  6 — The  Smokestack  at  noon  when  least  steam  is  visible. 


have  been  forced  down  into  the  ground  for  3  or  4  feet  at  the  Steam¬ 
boat  and  Safety  Valve,  and  from  these  most  of  the  steam  now 
escapes.  These  are  the  only  very  active  fumaroles  at  The  Geysers, 
and  even  these  are  quite  feeble  compared  to  those  in  many  other 
localities. 

Seventy-five  yards  or  more  east  of  Geyser  Creek  and  twice  that 
distance  south  of  Steam  Well  No.  2  (see  map,  fig.  1)  there  is  a  group 
of  small  vents  lined  with  sulphur  needles,  from  which  steam  is  noise- 


16 


lessly  escaping.  But  while  well-defined  fumaroles  at  The  Geysers  are 
few,  steam  and  gases  are  constantly  seeping  through  the  ground, 
especially  in  the  western  half  of  that  area,  and  on  cool,  damp  days, 
particularly  at  morning  (fig.  3)  and  evening,  large  clouds  of  con¬ 
densed  steam  may  be  seen  where  in  hot,  dry  summer  weather  it  is 
almost  entirely  absorbed  by  the  atmosphere. 


Fig.  7 — The  Safety  Valve  seen  at  midday. 

The  hot  springs  are  all  small  and  shallow,  in  fact  insignificant  in 
size;  the  largest  being  no  more  than  3  feet  in  diameter.  In  tempera¬ 
ture  they  are  comparatively  high,  as  few  springs  are  below  60°  C. 
and  the  hottest  are  at  boiling  temperature;  yet  nowhere  do  we  find 


Fig.  8 — The  Steamboat  Fumarole  in  morning  hours 


18 


signs  of  excessive  heat  like  violent  spouting  and  geyser  action.  Springs 
like  the  Witches’  Cauldrons  (fig.  9)  and  some  others  spout  at  times, 
but  rather  feebly,  exhibiting  on  the  whole  a  mild  thermal  activity  not 
unlike  the  fumaroles.  Physically  these  springs  vary  little  in  type; 
there  is  comparatively  little  clear  water;  most  of  it  is  turbid  or  muddy, 
though  mud  pots  and  mud  volcanoes  are  never  found  here.  The  sedi¬ 
ments  are  always  loose  but  never  plastic,  and  no  sinters1  of  any  kind 
are  in  process  of  deposition. 

As  many  hot-spring  districts  owe  their  distinctive  appearance  in 
great  measure  to  the  nature  of  the  sinter  deposited  by  their  waters, 
the  problem  of  deposition — to  what  extent  it  is  a  matter  of  physical 
and  chemical  forces  and  how  far  it  depends  on  the  life  processes  of 
certain  organisms  like  algae — well  deserves  further  attention.  At 
The  Geysers  few  springs  contain  a  vegetable  growth — such  at  least 
as  is  apparent  to  ordinary  scrutiny;  a  very  few,  of  comparatively  low 
temperature,  are  choked  by  green  algae  which,  however,  seem  to  be 
exercising  no  influence  on  mineral  deposition. 

As  in  so  many  other  hot-spring  districts,  the  odor  of  hydrogen 
sulphide  is  quite  generally  prevalent,  and  occasionally  the  odor  of 
what  seems  to  be  ammonium  sulphide  is  detected.  About  the  acid 
springs  in  the  Geyser  Creek  canyon  and  at  the  Steamboat  group  there 
is  a  characteristic  and  disagreeable  odor  which  has  been  noticed  in 
other  similar  localities  and  which  so  far  has  not  been  traced  to  any 
known  substance.  Possibly  it  is  caused  by  some  organism. 

Most  of  the  springs  are  grouped  in  a  few  small  areas,  all  of  which 
are  probably  determined  by  the  drainage.  The  majority  occur  in 
Geyser  Creek  canyon,  one  tiny  group  is  found  close  to  the  Steamboat 
Fumarole,2  while  a  third  group  rises  near  the  base  of  the  slope  to  the 
south  of  the  Steamboat  and  discharges  directly  into  Sulphur  Creek. 

In  the  hottest  part  of  Geyser  Creek  canyon  nearly  opposite  Steam- 
wells  1  and  2,  two  active  springs  rise  in  the  western  edge  of  the  little 
creek  (fig.  9).  The  Witches'  Cauldrons,  as  they  are  called,  are  charac¬ 
terized  by  a  strong  emission  of  gas  and  by  high  temperature  and 
spouting  when  they  are  not  chilled  by  excess  of  invading  stream 
water,  but  their  most  remarkable  feature  is  the  fine  black  sediment 
(fig.  10),  which  by  a  chemical  process  is  constantly  forming  in  them 
and  which,  discharging  into  the  little  stream,  transforms  it  to  an  inky 
fluid  whose  jet-black  current  flows  on  for  some  little  time  before  sedi¬ 
mentation  restores  the  water  to  its  natural  appearance — a  phenom¬ 
enon  never  observed  by  the  authors  in  any  other  place. 

Boiling  springs  containing  a  similar  sediment  are  found  at  several 
other  points  in  the  neighborhood — some  within  the  area  and  some 
outside. 

1  It  is  just  possible  that  the  “Arsenic”  spring,  which  is  quite  unimportant,  is  depositing  sinter; 
nothing  but  its  water  was  examined. 

2  The  largest  spring  is  marked  Teakettle  on  the  map. 


OF 

;  * 


Fig.  9 — At  right  and  left  in  foreground  are  two  bubbling  springs  known  as  the  Witches’  Cauldrons.  Photo  taken  when  inundated 


Fig.  10 — Looking  down  on  Witches’  Cauldrons  from  above.  Note  effect  of  inky  precipitate. 


F id.  11 — Acid  springs  in  overhanging  east  bank  of  Geyser  Creek. 


99 


The  most  numerous  group  of  springs  at  “The  Geysers'’  occurs  on 
the  east  bank  of  Geyser  Creek,  a  little  less  than  halfway  down  the 
canyon.  Here  the  receding  bank,  which  is  pretty  thoroughly  decom¬ 
posed  by  the  chemical  action  of  the  waters,  has  formed  a  bench  6  or 
8  feet  above  the  stream  level,  15  or  20  feet  in  breadth  and  perhaps 
125  feet  in  length,  along  which  are  ranged  in  a  row  a  dozen  or  more 
small  springs.  Most  of  the  springs  are  set  into  the  bank  (figs.  11,  12, 


Fig.  12 — “Washtub,”  Geyser  Canyon. 

13)  which  overhangs  some  of  them.  The  waters  are  all  acid  and 
their  tiny  effluents  in  the  early  summer  of  1925  kept  the  bench  wet 
with  hot  acid  water  so  ruinous  to  shoe  leather.  Under  favoring  con¬ 
ditions  this  bench  is  incrusted  with  salts.  At  the  Devil’s  Pulpit  there 
is  a  small  spring  sometimes  known  as  the  Punch  Bowl,  but  more 
appropriately  marked  on  the  old  map  as  the  Devil’s  Teakettle,  for  it 
throws  out,  with  a  pulsating  action,  a  little  shower  of  water  like  a 
sprinkler,  to  a  distance  of  5  or  6  feet.  The  springs  of  the  Steamboat 
group,  only  half  a  dozen  in  all,  carry  exceptionally  little  water  even 
for  this  semi-arid  region,  and  some  of  them  dry  up  in  hot  weather. 

On  the  lower  slope  of  the  eastern  half  of  The  Geysers  area,  not  far 
above  Sulphur  Creek,  there  are  half  a  dozen  warm  seepages  (  tem¬ 
perature  50°  to  60°)  occupying  as  many  shallow  gullies,  which  dis¬ 
charge  in  the  aggregate  considerable  water.  The  largest  supplies  the 
bath  house.  The  Magnesia  Spring,  long  held  in  repute  for  its  medic¬ 
inal  qualities,  emerges  on  the  hillside  not  far  to  the  west  and  at  about 


23 


the  same  level.  A  short  distance  upstream  from  the  bath  house  sev¬ 
eral  distinct  springs  of  much  higher  temperature  rise  in  the  bed  of 
Sulphur  Creek.  They  are  submerged  at  high  water,  but  when  summer 
is  well  advanced  the  creek  recedes  and  the  springs  can  be  tested  with¬ 
out  difficulty.  These  and  the  other  springs  of  this  group,  so  far  as 
tests  have  been  made,  are  alkaline. 


Fig.  13 — One  of  chain  of  springs  along  Geyser  Creek. 

TEMPERATURES  AT  THE  GEYSERS 

In  the  summer  of  1924  a  comparatively  large  number  of  ground 
temperatures  were  taken  at  The  Geysers  and  its  environs.  Small 
holes  were  dug  to  depths  varying  from  15  inches  to  4  feet  and  the 
temperatures  in  them  were  measured  with  an  armored  maximum 
thermometer.  Variations  of  course  were  found,  but  a  majority  of  the 
observations  lay  between  98°  and  99°  C.,  certainly  a  little  higher  than 
the  hottest  springs  and  fully  as  high  as  the  temperature  of  boiling 
water  for  the  prevailing  pressure.  The  reader  should  not  gain  the 
impression  that  such  temperatures  were  found  close  to  the  surface 
over  the  whole  area  covered  by  the  map;  places  showing  the  effects 
of  volcanic  gases  were  generally  chosen  for  the  tests.  Since  then,  how¬ 
ever,  highly  abnormal  temperatures  have  been  discovered  at  greater 
depths  in  spots  which  at  the  time  of  our  surface  exploration  showed 
no  signs  of  subterranean  heat. 

The  great  majority  of  the  natural  vents  are  not  of  sufficient  size 
to  admit  a  thermometer:  indeed,  they  are  better  described  as  gas 


24 


seepages  rather  than  vents.  The  fumaroles  grouped  on  the  slope  east 
of  Geyser  Creek  (see  map)  are  better  defined,  but  no  temperatures 
in  any  of  them  surpassed  that  of  boiling  water.  The  same  is  true  of 
the  Smokestack,  though  at  the  time  its  temperature  was  taken  it  was 
hardly  possible  to  make  a  satisfactory  observation  on  account  of  the 
difficulty  of  getting  close  to  it.  Slightly  higher  temperatures  were 
found  at  the  Steamboat  and  Safety  Valve,  where  depths  of  about  3 
feet  could  be  reached.  The  temperature  at  the  Steamboat  was  102°  C. 
The  readings  of  three  maximum  thermometers  and  a  calibrated 
thermocouple  were  compared  in  this  vent  and  found  to  be  almost 
identical.  At  the  Safety  Valve  many  observations  were  made,  but 
only  one  of  them  showed  a  temperature  as  high  as  102°.  This  was 
the  very  highest  temperature  outside  the  steam-wells  that  was  found 
in  the  whole  district.  It  should  be  remarked  that  the  steam  flow  in 
both  these  fumaroles  is  much  stronger  than  it  is  in  any  other  natural 
vent  at  The  Geysers,  with  the  possible  exception  of  the  inaccessible 
Smokestack.  On  June  27,  1925,  the  temperature  at  the  Steamboat 
was  101.5°,  while  the  highest  temperature  that  could  be  obtained  at 
the  Safety  Valve  was  only  98.5°.  This  was  possibly  due  to  failure 
to  reach  the  same  depth  as  before,  or  to  find  the  exact  path  of  the 
principal  steam  jet,  or,  possibly,  to  the  influence  of  a  larger  body  of 
ground  water, — in  any  case  the  difference  is  not  important. 

In  the  springs  three  or  four  series  of  temperature  measurements 
were  made.  Unfortunately  those  of  1924  were  lost  and  only  a  few  of 
them  can  now  be  recalled.  Two  series  were  made  in  1925 — the  first 
on  May  22,  almost  immediately  following  a  period  of  rainfall  which 
for  ten  days  prior  to  May  20  had  been  heavy  enough  to  fill  the 
streams,  wash  the  roads  and  leave  rain  pools  in  favorable  situa¬ 
tions.  This  was  at  the  end  of  an  unusually  wet  season.  The 
second  series  was  made  on  June  27  in  the  midst  of  a  very  hot, 
rainless  period  which  had  lasted  continuously  since  the  previous 
date. 

Inspection  of  table  1  shows  that  the  temperatures  in  this  locality, 
as  remarked  before,  are  comparatively  high — a  fact  which  is  readily 
understood  when  the  high  ground-temperatures  are  remembered  in 
connection  with  the  semi-arid  character  of  the  country.  Out  of  the 
total  number  of  well-defined  springs,  about  30  in  all,  nearly  two-thirds 
reach  a  temperature  of  80°  C.  or  more,  and  about  half  surpass  90°  C., 
while  the  hottest  springs  are  within  1°  of  the  temperature  of  boiling 
water  for  this  locality.  Some  forty  or  fifty  barometric  observations 
were  made  here  from  May  to  July  1925,  when  pressures  were  found 
to  vary  from  709  to  720  mm.,  under  which  conditions  water  boils 
between  98.1°  and  98.5°  C.  During  the  same  time  the  hottest  springs 
reached  97.5°  C.  Those  who  are  familiar  with  hot  springs  are  aware 
of  the  fact  that  they  often  boil  vigorously  at  temperatures  a  number 


of  degrees  below  the  true  boiling  point,  owing  to  the  fact  that  the 
atmospheric  pressure  is  partly  counterbalanced  by  the  gases  other 
than  steam  which  are  escaping  at  the  surface  of  the  water. 


Table  1. — Temperatures  of  hot  springs  and  fumaroles,  The  Geysers,  Sonoma  County, 

California. 


Place 

Date 

Tem¬ 

perature 

0  C. 

Date 

Tem¬ 
perature 
°  C. 

1925 

1925 

Geyser  Creek,  above  No.  13 . 

May  22 

17.5 

June  27 

42.0 

Do.  below  No.  3 

21  0 

Gevser  Creek,  near  outlet  [in  shade] . 

38 . 0 

Spring  No.  3,  “Boracic  Acid”  Spring . 

51.5 

55.3 

4 . 

93.0 

89.0 

5,  Devil’s  Kitchen . 

91.5 

85.3 

8,  35  ft.  above  the  last . 

63  0 

9,  15  ft.  above  No.  8 . 

72.0 

88.5 

10,  Liver  Spring  5  ft.  above  No.  9. 

89.0 

88.5 

11,  Washtub  15  ft.  above  No.  10.. 

95.5 

96.0 

12,  Tiny  spring  under  rock,  just 

west  of  No.  11 . 

97.5 

97.0 

Witches’  Cauldron-Lower  pool . 

40.0 

96.5 

Witches’  Cauldron-Upper  pool . 

28.5 

94.0 

Devil’s  Teakettle . 

95.2 

97.5 

Spring  No.  29,  New  spring  east  of  Steam 

Well  No.  2 . 

79.0 

53.5 

30,  New  spring  close  to  No.  29 

(black  sediment) . 

97.5 

95.0 

Group  31,  Teakettle . 

May  23 

95.0 

88.0 

Do.  Spring  just  below  Teakettle . 

70.0 

68.0 

Do.  Spring  just  above  Teakettle . 

96.0 

96.8 

Do.  Tiny  spring — just  above  the  last — 

(blank  sediment! 

95  0 

Do.  Small  sulphur  spring  2  ft.  south 

of  the  last 

84.0 

Spring  No.  32,  South  of  Well  5  and  below 

road  (blank  sediment) 

89  0 

Bathhouse  Spring  east  side  of  tank . 

50.0 

52.0 

Hot  rivulet  runninc  into  tank,  past  side 

54  0 

Seepage  in  gulley  just  west  of  Bathhouse 

Spring . 

40 . 0 

Fumarole  near  the  last . 

95.0 

Spring  No.  33,  Spring  in  bed  of  Sulphur 

Creek  above  bathhouse,  north 

side  of  creek . 

84.5 

Spring  No.  34,  Spring  in  bed  of  Sulphur 

Crppk  (blank  sediment! . 

88 . 0 

Magnesia  Spring . 

60 . 5 

60.5 

Lemonade  Spring 

86.0 

Mud  Spring  above  Lemonade  Spring 

May  27 

64.0 

Ink  Spring . 

May  22 

79.0 

Steamboat  Fumarole 

May  °7 

101.5 

Safety  Valve  Fumarole 

98.5 

Referring  again  to  the  table,  it  will  be  seen  that  during  this  time 
a  few  springs  were  practically  constant  in  temperature;  that  most 
of  them  showed  variation,  but  smaller  than  might  be  expected 


26 


when  the  wide  seasonal  difference  between  the  two  dates  at  which 
the  observations  were  made  is  kept  in  mind;  and  furthermore  that 
the  change  is  not  always  in  the  same  direction.  The  large  tem¬ 
perature  rise  in  the  Witches’  Cauldrons  is  easily  explained  by  the  fact 
that  they  are  found  in  the  edge  of  a  creek  bed  in  which  the  water 
subsided  markedly  in  the  course  of  a  month.  The  small  temperature 
changes  shown  by  most  of  the  springs  are  quite  at  variance  with 
changes  in  the  springs  of  the  Lassen  National  Park  which  respond 
so  generally  to  seasonal  differences  that  we  were  led  to  the  conclu¬ 
sion  that  the  hot  springs  there  must  be  largely  supplied  by  ground 
water.1  Without  conceding  that  ground  water  does  not  constitute 
a  large  part  of  that  in  The  Geysers  springs  also,  it  must  be  admitted 
that  the  recorded  temperatures  form  no  solid  ground  for  the  affirm¬ 
ative  conclusion,  though  it  is  by  no  means  certain  that  a  compari¬ 
son  of  the  above  observations  with  winter  temperatures  would  not 
show  much  greater  differences. 

SURFACE  DRAINAGE  AND  ITS  EFFECT  ON  THE  SPRINGS 

The  majority  of  the  hot  springs  of  The  Geysers  come  to  the  surface 
at  low  points  where  drainage  water  would  be  expected  to  emerge;  all 
of  them  indeed  are  so  situated  that  if  they  were  cold  springs  one 
would  find  nothing  illogical  in  their  relation  to  the  topography.  Most 
of  them  occur  in  the  Geyser  Canyon,  the  bed  of  Sulphur  Creek,  or 
in  the  gullies  draining  into  these  from  the  mountain-side;  in  the 
unusual  cases  where  springs  issue  on  high  points  like  the  Devil  s 
Pulpit  or  the  Smokestack  there  is  always  still  higher  ground  above 
them  and  they  are  either  very  small  or  dry  up  entirely  in  the  hotter 
weather.  Steam  vents  on  the  other  hand,  while  they  sometimes  fol¬ 
low  the  creek  beds,  occur  also  in  situations  where  no  logical  relation 
to  topography  is  apparent. 

With  the  question  in  mind  as  to  what  extent  the  water  of  these 
springs  may  be  of  surface  origin,  the  observer  on  the  ground  can  not 
but  suspect  that  the  small  size  of  the  springs  and  their  meager  dis¬ 
charge  is  connected  with  the  total  amount  of  the  drainage.  For  half 
the  year  the  region  is  practically  rainless  and  though  considerable 
precipitation  takes  place  in  the  fall  and  winter  months,  the  run-off 
on  these  very  steep  slopes  is  doubtless  high,  and  in  the  dry  season  the 
parched  surface  of  the  ground  and  the  dwindled  volume  of  the  streams 
are  convincing  evidence  of  a  limited  body  of  ground  water.  Indeed, 
when  the  small  hot  springs  of  the  Coast  Mountains  are  contrasted 
with  those  of  a  region  like  the  Lassen  National  Park  or  more  strik¬ 
ingly  with  the  great  geyser  basins  of  the  world,  all  of  which  are  closely 

1  Volcanic  activity  and  hot  springs  of  Lassen  Peak,  A.  L.  Day  and  E.  T.  Allen,  Carnegie 
Inst.  Wash.  Pub.  No.  360,  p.  154,  1925. 


associated  with  large  supplies  of  ground  water,  their  character  appears 
but  the  natural  result  of  their  topographic  and  climatic  surroundings. 

Fortunately  The  Geysers  region  came  under  the  observation  of  the 
authors  in  two  successive  years  of  quite  unequal  precipitation.  The 
pronounced  drought,  beginning  in  the  autumn  of  1923  and  continuing 
throughout  the  year,  was  followed  in  the  autumn  of  1924  and  the 
winter  months  of  1924-5  by  a  season  of  exceptionally  high  rainfall. 
In  May  1925,  as  we  have  already  recounted,  the  swollen  condition  of 
the  streams,  the  general  occurrence  of  rain-pools,  of  occasional  land¬ 
slides  on  the  mountain  slopes  and  the  flourishing  condition  of  vege¬ 
tation  were  all  in  striking  contrast  to  the  aspects  of  the  country  in 
the  previous  year,  but  a  change  of  corresponding  magnitude  was  cer¬ 
tainly  not  perceptible  in  the  springs.  Those  in  Geyser  Creek  canyon 
appeared  to  be  of  about  the  same  level  as  they  were  a  year  earlier. 
Their  tiny  outlets  seemed  to  be  discharging  a  somewhat  larger  volume 
of  water  but  there  was  no  conspicuous  difference.  The  group  next  the 
Steamboat  Fumarole  seemed  to  contain  an  appreciably  larger  volume 
of  water,  and  the  seepages  on  the  southern  slope  of  the  area  above 
the  bath-house  were  unquestionably  carrying  more  water  than  they 
did  a  year  earlier.  Confirming  the  last  conclusion  the  temperature  of 
the  bath-house  supply  was  found  to  be  about  10°  lower  (50°  instead 
of  62 3  C.)  than  in  1924.  On  the  whole,  however,  the  visible  differ¬ 
ences  in  the  discharge  of  the  water  were  less  than  expected,  and  taken 
by  themselves  can  not  be  said  to  constitute  a  strong  argument  for  the 
predominance  of  surface  water  in  the  springs. 

At  the  time  these  observations  were  made,  a  number  of  other  facts 
bearing  on  the  same  problem  came  to  notice.  New  springs  appeared 
at  points  where  none  had  existed  in  the  dry  weather  of  the  previous 
year.  At  the  foot  of  a  steep  bank  near  the  trail  between  Wells  2  and 
4  (see  map)  two  springs  were  found,  about  10  feet  apart,  each  about 
18  inches  in  diameter.  The  eastern  one  was  spouting  to  the  height 
of  an  inch  or  two  at  a  temperature  of  97.5°,  contained  a  sediment  of 
black  mud  and  was  in  every  way  similar  to  more  permanent  springs. 
The  other  spring  had  a  temperature  of  79°.  A  depression  close  by 
contained  at  that  time  a  rain-pool  perhaps  30  by  30  feet.  At  a  later 
date  a  new  hot  spring  was  discovered  near  the  bath-house,  in  the  bed 
of  Sulphur  Creek.  The  volume  of  this  spring  was  considerable  and 
the  temperature  was  84.5°  C.  Warm  seepages  hitherto  unnoticed 
were  also  found  at  other  points.  Nearly  all  these  newly  found  springs 
occurred  in  bare  or  open  ground,  either  close  to  the  trail  or  close  to 
places  which  had  been  frequently  visited  and,  as  they  represent  pre¬ 
cisely  the  phenomena  sought  for,  it  is  inconceivable  that  they  should 
have  existed  in  1924;  or  if  they  existed  at  all  they  must  have  been 
discharging  so  little  water  as  to  have  attracted  no  attention.  It  is 
this  variation  in  flow  that  is  really  important  whether  it  ceases  alto- 


28 

gether  or  not.  In  the  barren  ground  on  the  narrow  summit  of  the 
Devil’s  Pulpit  (fig.  14)  immediately  to  the  north  of  Geyser  Canyon 
was  found  a  small  basin  2  or  3  feet  in  diameter  lined  with  the  black 


Fig.  14 — Geyser  Creek  canyon  looking  north  at  midday.  Devil’s  Pulpit  slightly  to 

left  of  center. 


mud  characteristic  of  many  hot  springs  in  this  locality.  There  was 
no  water  in  the  basin  at  that  date  (May  22),  but  the  ground  was  still 
steaming.  A  similar  find  on  the  summit  of  the  Smokestack  in  1924 


29 


has  been  mentioned  in  another  connection.  At  a  point  35  yards  north 
of  Well  No.  4  on  the  trail  from  Well  No.  2  to  the  Steamboat,  a 
fumarole,  less  active  now  than  in  former  years,  was  observed  repeat¬ 
edly  in  1924.  In  the  early  part  of  our  second  visit  (1925)  its  depres¬ 
sion  was  occupied  by  a  shallow  hot  spring  which  later  dried  up  and 
gave  place  to  a  steam  jet.  Other  phenomena  of  the  same  kind  and 
of  a  more  striking  character  have  been  observed  by  us  in  other  hot- 
spring  regions.  They  constitute  one  of  the  most  convincing  lines  of 
evidence  for  the  close  relationship  of  hot  springs  to  ground  water. 

DISCHARGE  OF  THE  HOT  SPRINGS  ON  GEYSER  CREEK 

It  is  hardly  a  practical  task  to  gage  the  individual  springs  at  The 
Geysers.  They  are  often  unfortunately  located  for  measurement,  and 
taken  separately  practically  all  are  of  insignificant  volume.  It  is  pos¬ 
sible,  however,  to  measure  the  aggregate  discharge  of  the  springs  on 
Geyser  Creek,  which  is  estimated  to  be  fully  half  of  the  total  outflow 
of  hot  water  at  The  Geysers  and  perhaps  considerably  more.  Pre¬ 
liminary  experiments  were  made  about  the  middle  of  June  1924.  At 
that  time  the  water  in  Geyser  Creek  was  so  low  that  the  discharge 
could  be  measured  directly.  Dams  with  outlet  pipes  carrying  the 
total  volume  of  water  were  built  across  the  creek  and  the  water  was 
caught  and  measured  in  vessels  of  known  capacity  while  the  time  was 
taken.  In  this  way  it  was  learned  that  at  that  time  the  discharge  of 
Geyser  Creek  near  its  mouth  was  only  about  17  gallons  per  minute, 
or  26,000  gallons  per  day.  At  a  point  nearly  opposite  the  Devil’s  Arm 
Chair  the  flow  was  practically  the  same,  while  just  below  the  Witches’ 
Cauldrons  it  was  only  about  12,000  gallons  per  day.  A  dam  built 
near  the  head  of  the  canyon  at  the  top  of  a  small  fall  indicated  that 
the  discharge  here  was  less  than  half  what  it  was  at  the  mouth,  but 
this  figure  was  not  trusted  on  account  of  leakage  in  the  dam  which 
could  not  be  stopped.  In  1925  the  measurements  were  continued. 
The  stream  was  then  so  high  that  the  method  thus  far  used  was 
deemed  impractical  and  small  weirs  were  adopted.  In  1924  tempera¬ 
ture  measurements  of  the  water  taken  all  the  way  up  the  creek  at 
intervals  of  25  feet  had  indicated  no  significant  influx  of  either  warmer 
or  colder  water  below  the  second  dam  opposite  the  Devil’s  Arm  Chair. 
In  1925  there  was  a  point  a  short  way  above  the  confluence  of  the 
canyon  with  the  ravine  mentioned  on  p.  11,  where  some  influx  of 
steam  or  hot  water  occurred,  but  it  must  have  been  a  verv  small 
fraction  of  the  total  hot  water  flowing  into  the  creek.  It  may  also  be 
noted  that  the  above-mentioned  ravine  was  dry  in  1924  though  not 
in  1925. 

Taking  these  facts  together,  the  most  advantageous  positions  for  the 
weirs  were  seen  to  be:  for  the  lower,  a  point  a  little  below  Spring  3 
(see  map),  and  for  the  upper  weir  a  point  opposite  the  Devil’s  Pulpit 


30 


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31 


about  30  yards  above  the  Punch  Bowl  (Devil’s  Teakettle  on  the 
map).  Between  these  two  points  Geyser  Creek  gets  practically  all 
its  influx  of  warm  water  and  in  the  drv  season  there  are  no  tributaries. 
There  may  have  been  a  very  slight  accession  of  cold  water  from  the 
gulley  between  the  Pulpit  and  the  Smokestack  on  the  earliest  dates 
given  in  the  table  below;  at  least  our  records  mention  a  little  rivulet 
seen  there  May  22,  but  it  was  very  slight  and  rapidly  dried  up. 
Table  2  gives  the  discharge  of  the  creek  at  the  two  points  mentioned 

3 

for  five  different  dates.  The  formula  of  Francis:1  Q  =  3.33  LIT  is 
used  in  the  computation,  where  Q  is  the  discharge,  L  is  the  length  of 
the  weir  and  H  the  head.  L  =  18.25  inches  and  L'  =  24  inches.  The 
accented  symbols  refer  to  the  upper  weir.  Q  —  Q'  is  therefore  the 
influx  of  hot  water  between  the  two  weirs.  The  results  may  be 
slightly  affected  by  evaporation,  but  inasmuch  as  the  distance  between 
the  weirs  is  only  250  yards  while  the  current  is  tolerably  rapid  and 
the  temperature  most  of  the  way  was  moderate  in  1925,  the  error  is 
believed  to  be  slight.  The  results  show  that  the  total  discharge  of 
the  springs  is  quite  limited  and  that  there  is  an  unmistakable  decline 
in  the  discharge  as  the  dry  season  advances,  though  the  variation  is 
by  no  means  as  great  as  that  in  the  stream.  Small  as  the  discharge 
is,  at  the  lowest,  42,640  gallons  July  4,  1925,  it  is  much  higher  than 
it  was  in  June  1924  when  the  total  discharge  of  the  creek  was  only 
26,000  gallons.  It  is  also  obvious  that  a  variation  so  small  and  gradual 
would  be  likely  to  be  missed  unless  actual  measurements  were  resorted 
to.  It  is  not  claimed  that  the  measurements  apply  exclusively  to  the 
actual  overflow  from  the  springs;  observation  indicates  that  water  is 
probably  oozing  from  them  even  when  they  show  no  visible  overflow, 
and  it  is  not  improbable  also  that  the  above  figures  (Q  —  Q')  include 
some  water  not  belonging  to  any  well-defined  spring.  But  the 
measurements  do  show  clearly  that  a  body  of  ground  water  varying 
in  volume  with  the  season  is  constantly  reaching  the  surface  along 
this  creek,  water  none  of  which  is  from  tributary  streams  and  most  of 
which  is  derived  directly  from  hot  springs.  A  part  of  the  water  of 
these  springs  is  therefore  of  surface  origin. 


THE  SPRING  WATERS 


Inasmuch  as  “The  Geysers”  is  one  of  the  oldest  health  resorts  in 
California,  the  composition  of  the  spring  waters  attracted  early  atten¬ 
tion.  A  considerable  number  of  them  were  analyzed  in  the  eighties 
by  Dr.  Thomas  Price  and  Dr.  Winslow  Anderson,2  whose  results  have 
been  translated  into  modern  form  by  Gertrude  E.  Goodman  and 
published  by  Waring  in  his  Springs  of  California .:i  They  have  been 


1  See  Horton,  U.  S.  Geol.  Surv.,  Water  Supply  Paper  No.  150,  p.  25. 

2  Mineral  springs  and  health  resorts  of  California,  by  Winslow  Anderson,  San  Francisco, 

3  U.  S.  Geol.  Surv.,  Water  Supply  Paper  No.  338,  pp.  86-87,  1915. 


1892. 


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28.1 

Temperature . 

Properties  of  reaction: 

Primary  salinity . 

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Constituents. 

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1  Calculating  the  boron  as  the  radical  BO2  in  the  alkaline  springs  we  should  have  59  and  16  instead  of  48  and  13  respectively. 


34 


reproduced  here  for  comparison  with  our  own,  which  are  tabulated 
in  table  3.  In  several  particulars  these  waters  are  unusual  and  possess 
considerable  interest  for  chemists  and  geologists.  In  the  dominance 
of  sulphates  and  the  almost  complete  absence  of  chlorides  they  recall 
the  waters  of  the  Lassen  National  Park.  Chlorides  are  present  in 
undoubted  traces,  but  much  ordinary  distilled  water  probably  con¬ 
tains  as  much.  Like  the  hot  springs  of  the  Lassen  National  Park  the 
majority  of  the  waters  are  acid,  but  here  the  resemblance  ceases. 
The  divergences  are  to  be  attributed  to  wide  differences  in  the  char¬ 
acter  of  the  rocks  in  the  two  districts.  As  serpentine  is  commonly 
exposed  at  The  Geysers  it  is  not  surprising  to  find  the  magnesium 
content  of  the  spring  waters  much  higher  than  the  calcium.  The 
derivation  of  the  magnesium  is  in  fact  fully  confirmed  by  an  exami¬ 
nation  of  the  serpentine,  which  in  most  places  is  found  to  be  in  process 
of  decomposition,  often  honeycombed  with  cavities  sometimes  as  large 
as  a  man’s  arm,  which  are  commonly  lined  with  salt,  of  which  sulphate 
of  magnesium  is  the  most  important  constituent.  The  cavities  are 
probably  due  largely  to  the  falling  out  of  constituent  parts  of  the 
conglomerate  which  have  been  loosened  by  chemical  action.  An 
analysis  of  the  serpentine  in  this  area  shows  that  except  for  calcium 
it  contains  nearly  all  the  constituents  found  in  the  spring  waters, 
even  to  the  secondary  constituents,  manganese,  nickel  and  chromium. 

Analysis  of  Serpentine.  Green  Metamorphic  from  The  Geysers  area. 


Si02 . 

.  42.24 

SiO, . 

.  48.22 

TiO> . 

.  none 

TiO, . 

.  1.34 

AI2O3 . 

.  1.33 

AI2O3 . 

.  14.40 

Cr203 . 

.  0.60 

Cr203 . 

.  0 . 06 

Fe203 . 

.  8.55 

Fe203 . 

.  2.68 

FeO . 

.  1.40 

FeO . 

.  7.74 

NiO . 

.  0.07 

NiO . 

.  0.02 

MnO . 

.  0.08 

MnO . 

.  0.16 

MgO . 

.  34.14 

MgO . 

.  5.99 

CaO . 

.  none 

CaO . 

.  10.52 

BaO . 

.  none 

BaO . 

.  0.02 

Na20 . 

.  none 

Na20 . 

.  5.40 

K20 . 

.  none 

KaO . 

.  0.20 

-HoO . 

.  0.47 

-  H,0 . 

.  0.31 

FHiO . 

.  11.10 

+HoO . 

.  2.76 

S . 

.  0.13 

S  . 

.  0.02 

COo . 

.  none 

C02 . 

.  none 

P205 . 

.  undet. 

P2O5 . 

.  undet. 

100.11 

99.84 

Less  02 . 

.  0.05 

100.06 

Manganese  in  small  quantities  is  no  doubt  present  in  many  spring 
waters  where  it  has  not  been  looked  for,  but  chromium  and  nickel  in 
appreciable  amounts  are  probably  rare  outside  the  Coast  Range. 
Very  unusual  is  it  to  find  spring  waters  so  low  in  the  alkalis;  many 
of  the  springs  contain  hardly  more  than  the  reagents  used  in  the 


separation,  as  several  blanks  have  shown.  The  absence  of  the  alkalis 
is  further  evidence  of  the  relation  of  the  waters  to  serpentine.  At  first 
sight  it  may  appear  strange  that  the  acid  waters  are  so  high  in  silica, 
in  this  locality  higher  in  fact  than  the  alkaline  waters — which 
seems  like  a  chemical  anomaly.  It  is  not  unusual,  however,  and  it 
may  be  added  that  silica  is  always  carried  into  solution  when  silicates 
are  decomposed  by  acids,  the  amount  depending  on  the  nature  of  the 
silicate,  the  concentration  of  the  acid  and  other  conditions.  All  the 
waters  carry  appreciable  amounts  of  calcium  and  the  acid  waters 
carry  aluminum  also  in  similar  amount.  The  calcium  must  originate 
from  some  other  source  than  serpentine,  and  while  some  aluminum  is 
found  in  the  serpentine,  it  averages  in  the  acid  springs  nearly  one- 
tenth  as  much  as  the  magnesium,  a  fact  which  indicates  that  some  of 
it  probably  has  another  source.  Calcite  occurs  in  the  sandstone  in 
small  amounts,  but  there  is  no  proof  that  the  waters  reach  it.  At 
least  one  lime-bearing  metamorphic,  a  fine-grained  green  stone,  an 
analysis  of  which  is  appended,  is  found  in  the  area.  The  rock  contains 
considerable  sodium,  however,  and  this,  as  we  have  seen,  is  found  in 
the  waters  in  very  small  quantity. 

Except  for  calcium,  aluminum  and  ammonium,  all  the  bases  are 
probably  derived  from  serpentine.  As  ammonium  is  the  chief  basic 
constituent  of  all  the  waters,  it  is  rather  remarkable  that  it  was 
entirely  overlooked  by  the  older  analysts.  Its  origin  can  be  traced 
directly  to  the  gases  and  will  be  discussed  in  that  connection  (p.  74). 

All  the  waters  were  very  carefully  tested  for  boric  acid  by  a  most 
reliable  method,  but  in  most  cases  the  amount  found  was  inap¬ 
preciable. 

The  alkaline  springs,  few  in  number  in  this  locality,  possess  no  dis¬ 
tinctive  characteristic,  such  as  size,  temperature  range,  peculiar  ther¬ 
mal  action  or  deposits  of  special  nature,  which  enable  the  observer  to 
distinguish  them  from  the  acid  springs.  The  sediments  of  some,  to 
be  sure,  are  colored  black  by  a  peculiar  sulphide  of  iron  which  has 
never  been  noticed  in  any  of  the  acid  springs,  but  the  occurrence  is 
not  general;  the  sediments  of  some  alkaline  springs  are  white.  By 
simple  chemical  tests,  however  (sensitive  litmus  paper  and  phenol- 
phthalein  solution),  the  field  observer  may  classify  all  the  waters 
except  those  close  to  neutrality. 

Reference  to  the  chemical  analyses  (table  3)  shows  that  the  alkaline 
waters  are  more  complex  in  composition  than  the  acid  waters,  so  far 
as  the  number  of  the  acid  radicals  is  concerned;  simpler,  however,  in 
the  number  of  bases.  The  first  point  is  a  consequence  of  the  chemical 
processes  involved  in  the  development  of  the  alkaline  waters;  the 
second  is  a  mere  matter  of  solubility.  The  distinctive  acid  radicals 
are  carbonate,  bicarbonate,  thiosulphate  and  sometimes  sulphide1  in 

1  Presumably  bisulphides  also  occur,  but  of  these  salts  little  is  known. 


36 


small  amounts,  and  the  alkalinity  is  due  chiefly  to  bicarbonate  of 
ammonium,  magnesium  and  calcium.  Owing  to  the  peculiar  character 
of  the  rocks  from  which  the  mineral  matter  is  derived  the  alkalinity 
is  only  slightly  dependent  on  the  alkali  metals,  while  owing  to  the 
composition  of  the  gases  it  is  dependent  in  considerable  measure  on 
ammonium.  An  inspection  of  the  equivalents  in  table  4  makes  these 
facts  clear. 

There  are  two  points  connected  with  the  composition  of  the  alkaline 
spring  waters  to  which  attention  should  be  especially  directed.  First 
the  acid  radical  S04,  which  is  practically  the  only  one  in  the  acid 
waters,  is  found  in  all  the  alkaline  springs  without  exception,  and 
reference  to  table  4  shows  that  the  equivalent  value  of  this  radical  is 
generally  as  high  or  higher  than  the  sum  of  the  radicals  which  are  the 
source  of  the  alkalinity.  Secondly,  not  only  the  concentration  of 
this  radical,  but  the  total  concentration  of  the  alkaline  waters  is  so 
much  lower  than  that  of  the  acid  waters  as  to  constitute  a  different 
order  of  magnitude.1  Both  these  points  are  important,  holding  as 
they  do  the  key  to  the  origin  and  development  of  the  alkaline  springs. 

A  minor  problem  of  some  interest  to  the  chemist,  on  account  of  its 
bearing  on  natural  processes,  is  the  relation  which  the  distinctive 
radicals  in  the  alkaline  waters  hold  to  one  another.  Since  bicarbonates 
lose  more  or  less  readily  a  portion  of  their  carbon  dioxide  and  pass 
into  carbonates,  and  since  soluble  sulphides  under  the  influence  of 
air  may,  under  some  conditions,  be  oxidized  to  thiosulphate,  it  is  a 
question  whether  the  carbonates  and  thiosulphates  found  in  the  earlier 
analyses  (1924)  were  original  constituents  of  the  water  or  the  result 
of  chemical  changes  occurring  in  transit  to  Washington. 

The  idea  occurred  to  us  that  the  amount  of  volcanic  gases  in  springs 
of  this  character  might  invariably  or  generally  be  of  such  a  magnitude 
as  practically  to  exclude  air  and  prevent  the  formation  of  thiosul¬ 
phate;  and  of  such  a  magnitude  also  as  to  supply  sufficient  carbon 
dioxide  to  prevent  the  formation  of  carbonate. 

Assuming  this  to  be  true,  the  conditions  of  shipment  are  such  as 
to  make  it  quite  possible  that  the  secondary  constituents  in  question 
were  formed  in  transit.  In  sealing  water  samples  in  glass  bottles  it  is 
practically  necessary  to  leave  some  air  around  the  stopper  to  insure 
a  tight  seal  and  this  air  might  possibly  be  accountable  for  the  small 
amount  of  thiosulphate  found.  Furthermore  the  samples  had  been 
sealed  while  the  water  was  hot,  and  the  contraction  of  the  water  in 
cooling  had  resulted  in  a  reduction  of  pressure  inside  the  bottle  which 
would  of  course  increase  the  tendency  of  carbon  dioxide  to  escape  into 
the  vapor  space  and  leave  carbonate  in  the  water.  Several  additional 
samples  of  water  were  therefore  collected  in  1925  under  conditions 

1  To  this  rule  the  Ink  Spring,  found  outside  the  restricted  area  of  The  Geysers,  is  the  single 
exception,  but  only  two  of  the  acid  waters  possses  a  lower  concentration. 


37 


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38 


best  adapted  to  preserve  its  original  character,  and  the  analyses  were 
made  in  the  field  as  soon  after  collection  as  possible.  The  bottle  was 
first  filled  with  the  water  of  the  spring.  Then  by  a  simple  device  the 
bottle  was  allowed  to  suck  in  through  a  glass  tube  more  spring  water 
as  fast  as  it  cooled.  The  cooling  was  hastened  by  a  pail  of  cooler 
water.  Finally  just  enough  water  was  removed  to  keep  the  stopper 
dry  as  it  was  sealed  in. 

The  tabulated  results  of  analyses  made  in  the  field  laboratory 
include  no  carbonate,  while  two  of  the  samples  collected  previously 
without  special  precaution  contained  small  amounts,  so  that  unless 
conditions  in  the  springs  had  changed,  carbonate  was  not  an  original 
constituent  of  the  waters.  Since  that  time,  however,  a  large  number 
of  field  tests  made  in  California,  Nevada  and  the  Yellowstone  Park 
have  shown  that  carbonate  is  a  common  constituent  of  hot  springs 
though  many  contain  bicarbonate  only.  The  tabulated  results  show 
that  thiosulphate  is  an  original  constituent  of  two  springs  in  The 
Geysers  district;  one  of  them  outside  the  area  proper. 


Date 

hco3 

C03 

S 

S203 

Magnesia  Spring . 

1924 

341 

16 

none 

none 

1925 

377 

none 

none 

none 

Bath-house  Spring . 

1924 

275 

10 

none 

none 

1925 

282 

none 

none 

none 

Ink  Spring . 

1924 

167 

none 

trace 

2.3 

1925 

336 

none 

present 

5.6 

New  Spring . 

1925 

53 

none 

none 

58 

It  appears  therefore  from  the  results  that  there  is  no  uniformity  in 
the  amount  of  volcanic  gases  in  individual  hot  springs — even  those 
of  the  same  district — and  that  the  amount  of  gas  is  frequently  insuffi¬ 
cient  to  prevent  the  chemical  changes  just  considered.  The  source  of 
the  alkaline  springs  will  be  discussed  further  on  pp.  78-82. 

SALTS 

In  dry  weather  the  ground  at  The  Geysers  and  other  hot  areas  in 
the  neighborhood  is  more  or  less  incrusted  with  thin  patches  of  salt 
(fig.  15)  many  samples  of  which  were  collected  in  the  search  for  evi¬ 
dence  on  sources  or  genetic  conditions,  especially  such  as  might  throw 
light  on  the  ultimate  problems  in  hand.  In  some  places  appearances 
indicate  that  the  salts  are  derived  from  hot-spring  seepages  which 
evaporate  under  the  influence  of  the  warm  ground  and  dry  air.  This  is 
judged  to  be  the  source  of  the  salts  which  gather  on  the  bench  by  the 
little  chain  of  springs  in  Geyser  Creek  canyon  (see  p.  22) ;  in  general, 
however,  the  salts  occur  on  comparatively  high  ground  or  on  steep 
slopes  where  there  are  no  springs  but  where  the  odor  of  hydrogen 


39 


sulphide,  the  presence  of  steam,  or  the  high  temperature  of  the 
ground  indicate  that  they  are  the  direct  product  of  fumarole  activity 
or,  to  be  more  specific,  a  decomposition  product  of  the  surface  rocks, 
the  active  agent  in  which  process  is  sulphuric  acid  originating  from 
the  oxidation  of  hydrogen  sulphide  in  the  volcanic  gases.  A  unique 
occurrence  of  salts  was  found  beneath  an  overhanging  bank  opposite 
the  Devil’s  Pulpit  in  Geyser  Creek  canyon,  where  in  May  1925 
dripping  solutions  had  resulted  in  the  formation  of  stalactites — one 
of  which  had  reached  9  inches  in  length.  They  consisted  principally 
of  epsom  salt.  Speaking  generally,  the  salts  are  mixtures  chemically 
similar  to  those  found  by  analysis  in  the  spring  waters;  that  is  to  say, 


Fig.  15 — Salt  incrustations  beside  Steamboat  Fumarole. 


they  are  characterized  by  a  preponderance  of  ammonium  and  mag¬ 
nesium  sulphates  with  similar  secondary  constituents,  and  by  almost 
complete  absence  of  alkalis.  Aluminum  and  iron,  usually  in  the 
ferric  state,  occur  in  comparatively  small  amounts.  Chromium  has 
not  been  noticed  and  calcium  has  been  found  only  in  traces  among 
the  salts. 

Optically  the  salts  often  consist  of  complex  aggregates  of  interlacing 
crystals,  many  constituents  of  which  have  not  been  recognized,  but 
several  occurrences  for  one  reason  or  another  have  been  more  care¬ 
fully  studied  and,  for  indispensable  aid  in  this  work,  we  are  indebted 
to  F.  E.  Wright  and  H.  E.  Merwin. 


40 


Many  visitors  at  The  Geysers  have  probably  noticed  in  the  field 
small  spots  of  a  vivid  green  color  in  certain  of  the  salt  patches.  They 
are  quite  conspicuous  and  characteristic  of  the  locality.  The  color 
seems  to  be  due  to  sulphate  of  nickel,  which  metal  in  amounts  of 
some  tenths  of  a  per  cent  has  been  found  in  many  of  the  salt  samples, 
particularly  in  one  which  showed  in  the  field  a  bright  green  color  and, 
though  most  of  it  on  more  careful  examination  proved  to  be  white, 
Wright  observed  a  segregation  of  a  green  constituent  which  was 
found  to  be  high  in  nickel.  The  color  certainly  is  not  due  to  chromium 
which  in  this  specimen  was  absent,  and  if  it  is  due  chiefly  to  ferrous 
iron,  practically  all  of  that  constituent  had  changed  to  ferric  iron 
before  the  sample  was  examined,  and  this  without  any  of  the  signs 
of  oxidation  which  are  generally  visible  in  such  cases. 


Fig.  16 — Magnesium  sulphate  occurring  in  cavities  of  serpentine. 


Voltaite,  a  relatively  stable  sulphate  of  dark-green  color  which  is 
probably  due  to  the  combination  of  ferrous  and  ferric  iron  which  it 
contains,  occurs  at  The  Geysers  in  comparatively  thick  loose  masses 
of  rather  large  crystals  intermixed  with  a  small  amount  of  other 
material.  It  was  identified  by  Merwin  in  a  sample  collected  close  to 
the  Teakettle  (near  the  Steamboat  Fumarole)  and  several  other 
spots  are  now  recalled,  the  peculiar  appearance  of  which  was  probably 
due  to  this  salt. 

More  important  than  any  of  these  occurrences  are  the  relatively 
copious  deposits  of  sulphate  of  magnesium  which  may  be  seen  in  half 
a  dozen  places  in  The  Geysers  area.  Its  significance  lies  in  the  fact 
that  it  forms  the  connecting  link  between  the  springs  and  the  serpen- 


Fig.  17 — Salts  encrusting  wall  rock  of  Devil’s  Kitchen  where  acid  ammonium  sulphates  were  found. 


tine  rock  which  supplies  to  the  waters  a  large  part  of  the  mineral 
matter  they  contain.  The  salt  often  occurs  in  cavities  in  the  serpen¬ 
tine  (fig.  16)  which,  under  the  disintegrating  influence  of  the  fumarole 
gases,  is  gradually  changing  into  it.  It  consists  of  white  lathlike 
crystals,  dull,  lusterless,  often  mealy  in  appearance.  The  following  is 
an  analysis  of  the  purest  of  several  samples  examined.  It  was  picked 
out  by  Merwin  with  the  aid  of  the  binocular  microscope. 


Found 

Cal.  for 
MgS04 . 5H20 

h2o . 

42.97 

42.80 

Mg . 

10.80 

11.55 

Ni . 

0  09 

Fe . 

0  18 

Mn . 

0  11 

Ca.  . 

0  09 

S04  (diff.) . 

45 . 76 

45 . 65 

The  crooked  form  of  the  fibrous  crystals  in  certain  samples,  resem¬ 
bling  as  they  do  the  ice  spicules  which  grow  up  from  the  capillary 
pores  of  loose  frosty  ground  in  winter  time,  strongly  suggests  similar 
conditions  of  growth.  Optical  study  reveals  a  pseudomorphic  struc¬ 
ture,  that  is,  each  large  crystal  is  made  up  of  numerous  smaller  kernels 
variously  oriented;  rarely  a  single  small  crystal  has  changed  bodily 
to  one  of  different  properties.  The  salt  is  probably  derived  by  loss  of 
water  from  the  higher  hydrate,  epsom  salt  (MgS04.7H,>0).  Hygro- 
metric  measurements  of  the  atmosphere  at  The  Geysers  are  wanting, 
but  the  rather  low  dissociation  pressures1  of  epsom  salt  make  it  prob¬ 
able  that  the  warmth  of  the  ground  as  well  as  the  dryness  of  the 
atmosphere  is  instrumental  in  the  formation  of  the  pentahydrate 
above  described.  There  is  no  mystery  about  the  occurrence  of  the 
higher  hydrate  at  one  particular  spot,  for  there,  as  has  been  stated, 
an  excess  of  cool  water  was  present. 

Two  other  salts,  always  intimately  associated  in  hard  white  or 
light-brown  formless  lumps,  occur  at  several  points  in  this  fumerole 
field,  and  though  inconspicuous  they  are  of  considerable  interest 
because  of  the  light  they  throw  on  the  chemical  conditions  to  be  found 
in  such  localities.  These  salts  incrusted  the  wall  rock  of  the  spring 
known  as  the  Devil’s  Kitchen  on  Geyser  Creek  (fig.  17;  see  map); 
the  ground  above  the  Devil’s  Arm  Chair  (fig.  18)  and  the  bank  close 
to  the  Teakettle  where  it  was  observed  in  1922  and  also  in  1924. 
Chemical  analyses  were  made  of  the  purest  portions  of  several  samples. 
Like  all  other  salts  which  were  analyzed  they  were  dissolved,  filtered 
from  silica,  etc.,  and  the  solution  was  made  up  to  a  known  volume. 

1  Frowein,  Zeit.,  phys.  Chem.  1,  13,  1887;  Cohen,  Arch.  Neerland  (2)  5,  295,  C.  B.,  1901 
vol.  1,  772. 


Fin.  18 — Slope  above  Devil’s  Arm  Chair.  One  of  localities  for  acid  ammonium  sulphates. 


44 


aliquot  parts  of  which  were  used  in  analysis.  In  the  present  instance 
the  results  were  corrected  on  the  assumption  that  the  small  quantities 
of  magnesium  and  ferric  iron  found  were  in  combination  with  am¬ 
monium  as  double  sulphates,  but  the  corrections  are  unimportant; 
the  ratios  are  little  changed  (see  table  5).  All  the  samples  are  clearly 


Table  5. — Analysis  of  ammonium  acid  sulphates ,  The  Geysers,  Sonoma  County, 

California. 


Sample 

3 

0 

00 

t— • 

82 

10 

Weights 

Equiv. 

Weights 

Equiv. 

Weights 

Equiv. 

H . 

0 . 0046 

0.0046 

0 . 0029 

0 . 00290 

0 . 00495 

0 . 00495 

iN  H4 . 

.2145 

.01190 

.1580 

.00876 

.2350 

.01303 

Mg . 

.0013 

.00011 

.0090 

. 00074 

.0010 

. 00008 

Ni . 

Fe'" . 

.0040 

.00021 

.  0035 

.00019 

.0040 

.00021 

Sum 

.0168 

.0128 

.01827 

SO4 . 

.8115 

.0169 

.6160 

.0126 

.8795 

.01831 

Corrected  results. 


1 

Sample  No.  81 

82 

10 

Weights 

Equiv. 

Weights 

Equiv. 

Weights 

Equiv. 

H . 

0.0046 

0 . 0046 

0.0029 

0 . 0029 

0 . 00495 

0 . 00495 

NH4 . 

.2113 

.0117 

.  1435 

.00795 

.2322 

.01287 

S04 . 

.7875 

.0164 

.  5329 

.01109 

.  8578 

.01786 

Ratios  found 

Ratios  in  the  pure  salts 

Sample  81 . 

H  :  NH4  :  S04 

H  :  NH4  :  S04 

1  :  2.54  :  1.78 

1  :  2.74  :  1.91 

1  :  2.60  :  1.80 

1:1:1  NH4HSO4 

1:3:2  NH4HSO4.  (NH4)2S04 

Sample  82 . 

Sample  10 . 

ammonium  acid  sulphates  in  which  the  acidity  is  less  than  that  of 
NH4HSO4  and  more  than  that  of  (N^^SCh.NILHSCh.  At  first  the 
latter  salt  was  the  only  one  detected  by  the  microscope,  but  careful 
observation  showed  that  on  dry  days  another  salt  in  long  hairlike 
crystals  grew  out  of  the  moist  surfaces  of  the  lumps,  and  these  crystals, 
as  Merwin  found,  possessed  the  refractive  indices  of  the  simpler  salt 
NH4HSO4.  In  more  humid  weather  the  hygroscopic  nature  of  the 
substance  reduced  it  to  a  syrupy  solution.  The  material  collected  is 
not  therefore  a  definite  compound  as  the  constancy  of  the  analyses  at 


45 


first  led  us  to  believe,  but  a  mixture  of  the  two  acid  ammonium 
sulphates. 

These  salts  are  derived  from  the  volcanic  gases  reacting  with  the 
oxygen  of  the  air  (see  p.  78).  The  interesting  point  about  their 
genesis  in  this  connection  is  the  high  acidity  necessary  for  their  forma¬ 
tion;  the  less  acid  salt  crystallizes  according  to  Dorp1  only  from 
solutions  which  contain  as  much  as  16  per  cent  sulphuric  acid,  while 
the  simpler  salt  (NH4HS04)  crystallizes  from  solutions  containing  not 
less  than  33  per  cent  acid.  We  have  confirmed  the  latter  result,  ap¬ 
proaching  the  boundary  curve  between  the  two  salts  from  opposite 
directions,  that  is,  the  salt  NPTHSCh  was  crystallized  from  mixtures 
where  it  preceded  or  followed  the  double  salt.  The  limiting  concen¬ 
tration  of  sulphuric  acid  was  found  to  be  33.86  per  cent  and  33.72  at 
22°,  while  Dorp  found  33.84  per  cent  at  30°.  It  is  therefore  certain 
that  surprisingly  high  concentrations  of  sulphuric  acid  may  occur  in 
nature  where  the  climate  is  sufficiently  arid.  Rock  decomposition 
would  doubtless  be  greatly  accelerated  under  such  conditions  and 
would  probably  be  relatively  rapid  with  much  lower  concentrations 
of  acid.  At  Lassen  Peak  the  authors2  found  evidence  of  two  stages 
or  types  of  rock  decomposition  which  were  conditioned  by  the  acid 
concentration;  the  one  yielding  kaolin  and  salts  free  from  aluminum 
sulphate,  the  other  conditioned  by  more  concentrated  acid  yielding 
not  kaolin  but  silica,  with  salts  in  which  aluminum  was  the  predomi¬ 
nant  metal. 

A  complete  list  of  the  minerals  which  have  been  identified  in  salt 
mixtures  collected  at  The  Geysers  is  given  below.  Some  of  them,  now 
interesting  chiefly  to  the  mineralogist,  may  perhaps  in  the  future 
supply  useful  information  in  the  analysis  of  problems  of  a  character 
similar  to  those  here  discussed. 

(NH4)2S04 .  MgS04 . 6H2O — Boussingaultite  or  Cerbolite 
(NH4)2S04 .  Ab(S04)3 . 24H2O — Tschermigite 
MgS04 .  Al2(S04)3 . 22H2O — Pickeringite 
MgS04.5H20* 

NH4HS04.(NH4)2S04* 

NH4HSO4* 

Formula  uncertain — Voltaite 
Al2(S04)3. 16H20 — Alunogen 

*  These  three  minerals  seem  not  to  have  been  found  in  nature  before. 

SEDIMENTS 

Hot-spring  sediments  are  the  “insoluble”  products  of  rock  decom¬ 
position,  precipitates  formed  either  in  the  springs  themselves  or,  in 
some  cases  perhaps,  in  the  spring  waters  before  they  reach  their 
outlets.  Loosely  embedded  fragments  of  partially  altered  rock  or 
rock  minerals  often  occur  with  them.  The  sediments  in  this  locality 

1  Zeit.  Phys.  Chem.  73,  284,  1910.  2Day  and  Allen,  op.  cit. ,  p.  140. 


46 


47 


are  generally  loose,  fine-grained,  11011-plastic,  sometimes  gelatinous, 
muds,  usually  white  or  whitish  but  colored  at  times  by  sulphur,  oxide 
of  iron  or  black  sulphide  of  iron ;  the  compact  deposits  properly 
termed  “sinter"  are  never  found.  The  character  of  the  sediments  is 
evidently  the  result  of  local  conditions,  for  true  sinters  occur  in  a 
number  of  places  on  the  same  side  of  the  St.  Helena  Range.  Less 
than  half  a  mile  to  the  west  of  The  Geysers  near  the  border  of  hot 
ground  is  a  small  area  of  calcareous  sinter,  embedded  in  which  straws, 
acorns,  etc.,  prove  it  to  have  been  formed  at  the  surface.  Twenty-five 
miles  to  the  southeast,  a  small  deposit  of  siliceous  sinter  occurs  at 
Calistoga,1  and  thirty  miles  northwest  of  The  Geysers,  the  Vichy 
Springs,  near  Ukiah,  are  depositing  calcareous  sinter  at  the  present 
time.  The  conditions  which  determine  the  presence  or  absence  of 
sinter  in  hot-spring  deposits  is  a  problem  of  considerable  interest,  but 
a  fuller  knowledge  of  the  subject  will  be  necessary  before  it  can  be 
solved. 

Chemical  analyses  of  the  spring  sediments  at  The  Geysers  (see 
table  6)  show  that  silica,  alumina  and  volatile  matter,  including  water 
and  sometimes  more  or  less  sulphur,  are  the  chief  constituents.  Micro¬ 
scopic  analysis  proves  that  the  major  constituent  of  all  the  sediments 
is  opal,  but  as  the  material  is  isotropic  and  not  visibly  crystalline,  and 
as  the  only  measurable  optical  property  is  the  refractive  index,  no 
further  information  of  value  could  be  obtained  by  this  method.  It 
was  not  therefore  deemed  worth  while  to  complete  the  analyses. 

In  some  localities  there  is  a  striking  difference  between  the  sedi¬ 
ments  of  the  acid  and  alkaline  springs  even  when  the  two  classes  occur 
side  by  side,  but  at  The  Geysers  there  seems  to  be  no  distinctive 
difference  except  that  in  the  alkaline  springs  a  black  sulphide  often 
occurs  in  addition  to  the  substances  common  to  both.  In  the  analyses 
of  such  sediments,  the  sulphide  was  first  removed  by  dilute  nitric 
acid  and  is  not  included  in  the  table.  This  sulphide  is  rather  remark¬ 
able  both  physically  and  chemically.  It  is  black,  lusterless,  so  fine¬ 
grained  that  it  often  settles  very  slowly,  reveals  no  crystallinity  under 
the  microscope,  and  is  insoluble  in  hydrochloric  acid.  In  the  test  of 
several  samples,  iron  always  proved  to  be  the  principal  metallic  con¬ 
stituent  and  this  was  invariably  accompanied  by  a  small  amount  of 
nickel.  No  other  metal  was  found.2  The  ratio  of  nickel  to  iron  was 
determined  in  several  instances.  In  the  sulphide  of  the  Devils  Punch 

Bowl,  the  results  were  ^  ^  =  0.025;  while  in  the  black  mud 

Fe  0.0838 


collected  from  the  slopes  of  the  steaming  Smokestack,  which  is  of 

1  In  a  meadow  near  Pacheteau’s  Baths.  In  the  course  of  the  last  few  years  the  hot  springs 
which  deposited  this  sinter  have  ceased  to  flow — a  result  of  drilling  of  nearby  wells.  (Private 
communication  from  Mr.  A.  Rocca.) 

2  No  mercury  has  yet  been  detected  in  any  of  the  sediments,  though  this  area  lies  within  the 
limits  of  the  quicksilver  belt,  and  cinnabar  in  small  amounts  has  been  found  at  two  points.  It 
occurs  in  steaming  cracks  coating  opal. 


48 


essentially  the  same  nature  as  the  hot-spring  sediments,  the  nickel- 
iron  ratio  proved  to  be  only  0.011.  Both  the  iron  and  the  nickel  are 
probably  derived  chiefly  from  the  serpentine,  and  the  precipitation  of 
both  by  soluble  sulphide  in  the  waters  is  doubtless  in  progress  at  the 
present  time.  It  is  impossible  to  say  precisely  to  what  mineral  species 
this  insoluble  sulphide  is  to  be  referred.  Its  chemical  behavior  indi¬ 
cates  it  to  be  a  cryptocrystalline  pyrite  or  marcasite.  Coating  smooth 
pebbles  on  the  bottom  of  the  Witches’  Cauldron,  where  the  greatest 
amount  of  this  sulphide  occurs,  was  found  a  thin  crust  of  a  mineral 
having  the  color  and  luster  of  pyrite.  It  may  be  added  that  a  similar 
product  was  found  coating  numerous  lumps  of  clay  in  one  of  the 
alkaline  springs  of  the  Lassen  National  Park,  while  in  all  the  acid 
springs  of  the  neighborhood  the  sulphide  was  plainly  crystallized 
pyrite.  Evidently  pyrite  does  not  crystallize  well  from  waters  of 
this  character.  It  is  a  plausible  conclusion  from  the  data  before  us 
that  the  loose  black  sulphide  and  the  denser  bronze  crust  are  both 
cryptocrystalline  pyrite,  the  differences  in  properties  being  due  to 
difference  in  the  state  of  division. 

A  remarkable  fact  concerning  the  sediments  under  discussion  is  the 
absence  in  them  of  any  constituent  showing  plasticity,  birefringence, 
or  a  refractive  index  characteristic  of  kaolinite  or  any  other  of  the 
clay  minerals.  Kaolin  is  the  preponderant  constituent  of  the  sedi¬ 
ments  in  the  hot  springs  of  the  Lassen  National  Park  and  preliminary 
exploration  has  revealed  its  presence  in  at  least  a  number  of  places 
in  the  Yellowstone  Park.  It  should  be  noticed  at  the  same  time  that 
mud  pots  occur  in  both  these  localities,  though  they  are  not  found  at 
The  Geysers.  At  first  the  absence  of  kaolin  at  The  Geysers  was 
attributed  to  the  nature  of  the  rock;  feldspars  have  not  been  found 
here  in  the  zone  of  decomposition,  while  in  the  Lassen  Springs  the 
feldspars  and  volcanic  glasses  were  the  only  minerals  to  which  the 
formation  of  kaolin  could  be  traced.  But  this  conclusion  has  been 
nullified  by  the  subsequent  discovery  of  small  deposits  of  clay  in  the 
active  area  at  The  Geysers  though  not  in  the  springs  themselves. 
The  first  of  these  was  collected  at  a  point  about  50  yards  northwest  of 
the  Silver  Polish  bank.  It  was  a  very  plastic  mud,  having  nearly  the 
physical  and  chemical  properties  of  kaolinite.  The  color  is  blue,  much 
paler  when  dry,  and  the  average  refractive  index  (Wright)  is  a  trifle 
higher  than  ordinary  kaolinite.  The  analysis,  made  on  a  sample, 
from  which  the  soluble  matter  had  been  removed  by  water,  simply 
dried  on  the  steam  bath,  indicates  a  kaolinite  in  which  the  alumina 
has  been  partly  replaced  bv  chromic  oxide. 

Similar  substances  with  varying  percentages  of  chromium  have 
been  described  by  other  observers.1 

1  See  Wherry  and  Brown,  Am.  Mineral,  1,  63,  1916,  for  some  analyses  and  references.  See 
also  Journ.  fur  Prak.  Them.  34,  202,  1845. 


49 


Analysis  of  chrome-kaolinite  (miloschite) . 
Si02 . 

AI2O3 . 

Cr203 . 

Fe>03 . 

TiO> . 

NiO . 

MnO . 

MgO . 

Na20 . 

K20 . 

H>0 . . . 


40 . 00 
35.28 

2.42 

1.42 
0.05 

trace 

undet. 

0.08 

undet. 

undet. 

14.85 


100.21 

Another  occurrence  of  an  emerald-green  clay,  very  plastic  when 
wet  and  possessing  similar  optical  properties,  was  found  about  200 
yards  from  the  first  deposit.  A  partial  analysis  gave  Fe203  =  2.11 
per  cent,  Cr203  =  6.37  per  cent.  As  these  deposits  are  doubtless  of 
secondary  origin,  the  area  should  contain  some  mineral  from  which 
they  were  derived,  unless,  indeed,  it  can  be  shown  that  the  clay  was 
transported  from  a  distance,  which  appears  unlikely.  A  more  plausible 
hypothesis  in  explanation  of  the  absence  of  kaolin  from  the  springs 
at  The  Geysers — at  least  from  the  acid  springs — is  that  its  formation 
is  prevented  by  the  relatively  high  acid-concentration  which  is  found 
here.  In  the  Lassen  Springs  where  kaolin  is  the  chief  constituent  of 
the  sediments  the  acidity  is  generally  much  lower  and  the  waters 
usually  contain  only  traces  of  alumina,  but  in  the  warm  ground,  as 
previously  remarked,  in  many  places  where  silica  without  kaolin  is 
associated  with  salts  high  in  alumina  a  higher  concentration  of  acid 
is  indicated.  Furthermore,  at  The  Little  Geysers,  5  miles  from  The 
Geysers  on  the  same  hypothetical  fault  line,  where  the  rocks,  serpen¬ 
tine,  mica  schists  and  other  metamorphics  appear  to  be  sufficiently 
similar  to  those  at  The  Geysers,  but  where  the  acidity  of  the  spring 
waters  is  very  low,  the  sediments  are  high  in  alumina  (see  table  6), 
quite  plastic  and  possess  optical  characteristics — birefringence  and 
refractive  index — like  those  of  kaolinite  (Wright). 


Analysis  of  “ Silver  Polish” 

Si02 . 

A1203 . 

Fe203 . 

Ti02 . 

CaO . 

MgO . 

HoO . 


87.12 

2.20 

0.54 

6.00 

0.10 

none 

4.58 


100.54 

Though  not  a  hot-spring  sediment,  the  nonplastic  clay  from  the 
Silver  Polish  bank  occurring  on  the  trail  between  Wells  2  and  4  is 
doubtless  the  product  of  similar  agencies  and  may  properly  be  men¬ 
tioned  here.  It  is  nonplastic,  contains  little  alumina,  and  the  presence 


50 


in  it  of  free  sulphuric  acid  is  significant  of  its  origin.  Most  of  the 
material  had  the  refractive  index  of  opal,  but  certain  larger  brownish 
grains  possessed  a  distinctly  higher  index  and  these  disappeared  when 
the  material  was  fused  with  potassium  acid  sulphate,  leaving  nearly 
pure  silica.  The  brown  patches  were  probably  titanium  oxide  which 
the  analysis  shows  to  be  present  in  unusually  large  amount. 


Fig.  19 — Drilling  first  well.  The  Geysers,  1922. 


THE  STEAM-WELLS 

In  the  summer  of  1921  J.  D.  Grant,  of  Healdsburg,  California, 
began  drilling  on  the  hillside  to  the  east  of  Geyser  Creek  (fig.  19) 
with  the  hope  of  utilizing  the  steam  for  power.  At  that  time  he  was 
unaware  of  the  fact  that  a  similar  project  had  already  been  success¬ 
fully  attempted  at  Larderello  in  Tuscany,  but  he  had  become  im¬ 
pressed  with  the  constant  escape  of  steam  at  The  Geysers  and  its 


51 


relatively  high  temperature  at  the  surface  and  believed  that  both 
would  increase  with  depth.  The  results  confirmed  his  conclusion, 
though  the  first  shallow  bore-hole,  when  closed,  blew  out  the  casing 
and  was  abandoned.  In  the  following  summer  the  well  now  desig¬ 
nated  No.  1  was  drilled  on  the  east  bank  of  Geyser  Creek  and  reached 
its  present  depth  (203  feet)  in  September  1922.  For  the  first  80  feet, 


Fig.  20 — A  plank  across  mouth  of  casing, 
weighted  with  drill  rod  weighing  about 
a  ton,  fails  to  “hold  down”  steam,  1922. 


only  soft  material  was  encountered  but  the  steam-flowT  increased 
rapidly  with  depth  (fig.  20).  The  soft  surface  layer  consisted  of 
thoroughly  decomposed  rock  and  was  probably  similar  to  the  surface 
mud  well  exemplified  at  the  Smokestack  fumarole  just  opposite  on 
the  other  side  of  Geyser  Creek  (see  p.  14).  At  a  depth  of  80  feet 
the  sandstone  cap  was  struck  and  the  drilling  was  continued  through 
it,  after  which  an  8-inch  steel  casing  was  lowered  and  “anchored”  in 
the  rock  by  pouring  around  the  pipe  several  hundred  pounds  of 


molten  zinc  which  congealed  and  furnished  a  firm  and  tight  joint. 
Boring  continued  to  a  total  depth  of  203  feet  as  an  open  hole,  after 
which  the  well  was  closed  by  a  heavy  gate  valve  attached  to  the  top 
of  the  casing.  The  drilling  was  done  with  a  churn  drill  (fig.  20)  with¬ 
out  special  equipment,  the  steam  in  the  drill-hole  being  controlled  by 
admitting  a  stream  of  cold  water  to  condense  it.  At  the  end  of  each 
half  hour  or  so  the  well  was  allowed  to  “blow.”  Considering  that  the 
workmen  had  had  no  previous  experience  of  the  kind,  it  speaks  well 
for  their  skill,  initiative  and  perhaps  their  good  fortune,  that  the  work 
was  completed  without  serious  accident.  A  steam  gage  attached  to 
the  outlet  pipe  registered  a  pressure  of  62  pounds  to  the  square  inch 
when  the  well  was  closed. 


Fig.  21 — Drilling  second  well  with  steam  power  from  first.  Photo  obtained 

from  J.  D.  Grant. 


Encouraged  by  the  success  of  the  first  venture  to  continue  the 
undertaking,  on  October  18,  1922,  the  promoter  began  a  second  well 
within  50  feet  of  the  first,  carried  it  down  to  a  depth  of  318  feet  and 
closed  it  by  the  same  methods.  Steam  from  the  first  well  was  used 
without  filtering  or  other  treatment  to  furnish  power  for  drilling  the 
second  which  was  completed  July  20,  1923  (fig.  21).  The  gage  pres¬ 
sure  in  this  well  when  closed  showed  61  pounds.  Notwithstanding 
that  the  wells  were  so  close  together,  the  pressure  of  neither  seemed 
to  be  affected  by  the  discharge  of  the  other  (fig.  22).  Also,  when 
either  well  was  allowed  to  discharge  continuously  for  months  and 
then  closed  again  the  pressure  soon  attained  the  same  value  as  before. 


Fig.  22— Wells  No.  1  and  No.  2  discharging  into  atmosphere,  1924,  Excellent  view  of  Smokestack  Fumarole  right. 


54 


Beginning  in  the  summer  of  1924,  a  third  well  was  sunk  on  the 
extreme  border  of  the  hot  ground,  but  the  boring  was  discontinued 
at  a  depth  of  154  feet. 

During  the  first  two  years  a  local  stock  company,  “The  Geysers 
Development  Company,”  was  organized  to  carry  on  the  work  and 
Kingsley  G.  Dunn  of  San  Francisco  was  the  engineer  in  charge.  After 
some  vicissitudes,  this  pioneer  group  gave  way  to  a  new  organization 
with  stronger  financial  backing,  and  in  January  1925  drilling  was 
resumed  by  the  Diamond  Drill  Contracting  Company,  of  Los  Angeles, 
under  the  direction  of  J.  D.  Galloway,  engineer,  of  San  Francisco. 
This  Company,  using  a  rotary  equipment,  has  already  drilled  five 
holes,  numbered  successively  from  No.  4  to  No.  8,  of  which  Air.  Gallo¬ 
way  recently  presented  to  the  Engineering  Societies  of  New  York  the 
following  account : 

“During  the  first  seven  months  of  1925  four  wells,  No.  4,  No.  5,  No.  6  and  No.  7 
were  drilled.  These  four  wells  are  of  the  same  size  and  type  and  are  distributed  over 
an  area  about  550  feet  long.  An  open  hole  is  first  drilled  through  the  overburden  and 
into  rock  as  far  as  possible.  Into  this  hole  a  10-inch  wrought  steel  casing  is  set  and  the 
space  between  casing  and  the  walls  of  the  hole  filled  with  Portland  cement  grout.  After 
the  cement  is  set,  the  hole  is  then  drilled  deeper  into  the  rock  until  the  flow  of  steam  is 
good  and  then  an  inside  8-inch  wrought  steel  casing  inserted  and  the  space  between 
the  two  casings  is  filled  with  cement  grout  which  is  allowed  to  set.  After  this  the  well 
is  drilled  as  an  open  hole,  deeper  into  the  ground.  Data  on  the  four  wells,  No.  4,  No 
5,  No.  6,  and  No.  7,  are  given  in  the  following  table  with  some  for  No.  8  now  drilling. 


Wells 

No.  4 

No.  5 

No.  6 

No.  7 

No.  8 

Depth  of  10"  casing . 

153' 

91' 

83' 

103' 

68'  (15") 

Depth  of  8"  casing . 

256' 

203' 

208' 

176' 

160'  (12") 

Depth  to  bottom  of  well . 

451' 

416' 

487' 

483' 

* 

*  In  June,  1926,  this  hole  had  reached  a  depth  of  640  feet.  Both  pressure  and  temperature 
were  still  somewhat  lower  than  in  the  other  wells  and  drilling  was  still  in  progress  though  the 
rock  encountered  at  this  depth  was  a  hard  chert. — The  authors. 


“In  drilling  the  wells,  the  incoming  steam  is  condensed  by  the  stream  of  cold  water 
pumped  down  to  the  bottom  of  the  well  through  the  interior  hole  of  the  drill  stem.  The 
water  is  sent  down  under  pressures  up  to  250  pounds  per  square  inch,  and  under  the 
pressure  rises  to  the  top  of  the  well  outside  the  drill  stem  and  flows  off  through  a  side 
vent.  A  point  is  reached  when  the  cold  water  sent  down  comes  back  heated  to  near  the 
boiling  point  and  this  indicates  about  the  depth  required.  All  openings  on  the  well 
are  then  closed  and  the  drill  removed.  When  all  is  clear,  a  valve  at  the  top  is  opened 
and  the  hot  water  is  blown  from  the  well  by  the  geyser  effect.  Rocks  and  dust  are 
also  blown  out  and  it  takes  a  week  or  so  before  the  well  clears  the  passages. 

“In  drilling  through  the  rock,  the  hardness  varies  greatly.  The  drill  often  encoun¬ 
ters  fissures  or  fumaroles  in  its  passage  downward  and  these  underground  fumaroles 
indicate  the  presence  of  steam.” 


00 


The  opening  of  a  well  after  the  tools  are  removed  presents  an 
imposing  spectacle.  As  the  valve  is  opened  steam  and  hot  water  rush 
violently  out  with  a  great  roar,  rising  in  successive  leaps  like  a  geyser 
and  carrying  a  shower  of  sand  and  loose  rocks  which  bombard  the 
steel  frame  of  the  derrick  with  a  rattle  like  a  fire  of  musketry.  The 
column  quickly  reaches  its  maximum  height  of  200  to  300  feet  and 
in  a  few  moments  much  of  the  excess  water  and  loose  debris  are 
cleared  out,  leaving  a  huge  jet  of  intensely  hot,  roaring  steam  rushing 
from  the  well  at  high  velocity,  the  noise  of  which  can  be  heard  for 
several  miles  and  which  at  close  range  is  absolutely  deafening. 


Fig.  23 — Wells  open.  No.  1  and  No.  2  left,  No.  4  center,  No.  5  right  and  No.  6 
partially  closed  down  between  No.  4  and  No.  5.  1925. 


PRESSURE,  TEMPERATURE,  AND  OUTPUT  OF  THE  STEAM-WELLS 

While  the  method  employed  in  drilling  the  later  wells  is  obviously 
unsuited  to  the  determination  of  the  nature  of  the  rock  below  ground 
and  the  rise  in  temperature  with  depth,  the  log  of  the  earlier  wells 
yields  considerable  information  of  value,  but  its  consideration  belongs 
more  properly  in  another  section  of  this  paper  (see  pp.  82  and  88). 
In  depth  the  wells  vary  from  about  200  feet  to  nearly  650  feet.  The 
pressure  is  greater  in  the  deeper  wells  but  it  is  not  proportional  to 
depth ;  it  does  not  even  follow  the  same  order.  When  closed  and 
capped  the  pressure  in  different  wells  varies  from  60  pounds  to  275 
pounds  to  the  square  inch.  Mr.  Galloway’s  paper,  already  referred 
to,  contains  interesting  information  upon  this  point  also.  With  his 
permission  we  quote  once  more: 

“Characteristics  of  the  Steam — The  steam  pressure,  wells  closed,  varies  and  the  same 
is  true  of  the  quantity  of  steam  discharged  under  different  pressures.  In  the  case  of 
Wells  No.  G  and  No.  7,  the  wells  have  not  been  closed  long  enough  to  indicate  the  maxi¬ 
mum  pressure  but  it  is  believed  that  it  will  reach  300  pounds  to  the  square  inch.  Since 


56 


Well  No.  6  was  brought  in  with  an  initial  closed  pressure  of  about  250  pounds,  the 
static  pressure  in  other  wells  has  become  greater.  The  following  table  indicates  this. 


Wells 

No.  1 

No.  2 

No.  4 

No.  5 

No.  6 

No.  7 

Initial  Static  Pressure . 

Static  Pressure,  Sept.,  1925 . 

64  lbs. 
67 . 5 

67  lbs. 
67 . 5 

82  lbs. 
107 

143  lbs. 

211 

240  lbs. 
276 

198  lbs. 

“  Tests — Numerous  tests  of  the  quantity  of  steam  flowing  from  the  wells  have  been 
made.  Steel  discs  1/16"  thick  with  circular  openings  of  different  diameters  are 
clamped  between  flanges  and  the  steam  allowed  to  escape  until  such  time  as  the  pres¬ 
sure  becomes  constant  for  each  disc.  The  edge  of  the  opening  in  the  disc  is  rounded  to 
a  knife  edge  from  which  the  diameter  is  measured.  Pressures  are  read  by  calibrated 
test  gages  on  a  pipe  tapped  into  the  well  casing  a  few  feet  below  the  orifice  and  the 
quantity  of  steam  flowing  determined  by  Napier’s  formula. 


Fig.  24 — Wells  Nos.  4,  5,  6  and  7  discharging.  1925.  Photo  by  Kidd. 


“A  considerable  difference  in  quantity  and  pressure  of  steam  is  found  in  the  differ¬ 
ent  wells.  No.  1  and  No.  2,  which  are  some  distance  from  the  others  and  not  so  deep, 
stand  at  62  pounds,  gage-pressure  when  closed.  These  wells  are  close  together  and 
undoubtedly  connected.  Wells  No.  4,  5,  6,  7  (fig.  24)  driven  under  the  supervision  of 
the  writer  in  this  year  (1925)  show  wide  differences.  No.  4,  6  and  5  lie  in  a  straight 
line  in  the  order  named,  the  distance  between  No.  4  and  No.  6  being  275  feet  and  be¬ 
tween  No.  5  and  No.  6  the  same;  No.  6,  being  midway  between  No.  4  and  No.  5.  The 
maximum  static  pressure  for  No.  4  is  111  pounds,  of  No.  6,  276  pounds  and  of  No.  5, 
210  pounds.  It  is  probable  that  if  No.  4  were  drilled  deeper  it  would  deliver  greater 


0/ 

quantities  of  steam  and  register  greater  pressures.  Well  No.  7,  160  feet  distant  from 
’  No.  G  at  right  angles  to  the  line  of  the  other  wells,  is  somewhat  larger  than  No.  6  and  it 
is  thought  the  static  pressure  of  this  well  will  reach  300  pounds.  The  highest  yet 
reached  is  276  pounds  in  No.  6.  After  the  wells  have  been  open  for  a  time,  and  are 
then  closed,  the  pressure  rises  rapidly.  No.  6,  opened  for  several  weeks  and  dis¬ 
charging  at  about  150  pounds,  rose  to  270  pounds  pressure  in  50  minutes.  However, 
after  a  well  has  been  open,  it  takes  several  days  to  build  up  the  highest  pressure 
recorded. 


Fig.  25 — Well  No.  6.  Steamboat  Fumarole  in  fore¬ 
ground. 


“In  practice,  since  the  wells  must  deliver  steam  into  a  common  header,  the  quan¬ 
tity  of  steam  from  each  well  will  vary.  If  75  pounds  header  pressure  be  assumed, 
then  the  four  wells  described  will  deliver  the  following  quantities  of  steam  per  hour: 


Well  No.  4 
Well  No.  5 
Well  No.  6 
Well  No.  7 


7,500  lbs 
52,000 
38,000 
40,000 


137,500 


58 


“With  a  water  rate  of  27.5  pounds  per  kilowatt-hour,  condensing,  these  four  wells 
represent  a  switchboard  delivery  of  4,500  kilowatts,  after  allowing  10  per  cent  losses  in 
steam  in  transmission.  Each  well  on  the  average  will  thus  deliver  about  1,000 
kilowatts.”  (figs.  25,  26.) 


Fig.  26 — Well  No.  6  just  completed  and  shut  off.  1925. 


Up  to  the  present  time  the  opening  of  the  wells  has  had  no  visible 
effect  on  the  natural  fumaroles;  apparently  they  keep  on  steaming  at 
the  same  rate  as  ever  (fig.  27).  Neither  has  the  discharge  of  any  of 
the  wells  had  the  effect  of  diminishing  the  pressure  in  any  other, 
although  two  of  the  wells  are  within  50  feet  of  each  other.  On  the 
contrary,  Mr.  Galloway’s  record  reveals  the  fact  that  after  the  open¬ 
ing  of  No.  6  the  pressure  in  the  neighboring  wells  No.  4  and  No.  5 
increased  somewhat,  but  the  individual  pressures  are  still  far  apart 


Up  to  the  present  time  the  maximum  pressure  of  none  of  the  wells  is 
appreciably  affected  by  long-continued  discharge;  when  closed  again 
the  pressure  gradually  regains  its  former  value. 

In  the  summer  of  1925  with  the  kind  cooperation  of  Mr.  Galloway, 
a  series  of  temperature  measurements  with  corresponding  pressures 
was  made  in  the  wells.  An  8-inch  outlet  pipe  (horizontal)  which  was 
screwed  into  each  valve  body  was  tapped  to  admit  a  threaded  %-inch 
pipe  closed  at  the  inner  end  while  the  outer  end  also  could  be  closed 
by  a  removable  plug.  The  small  chamber  thus  formed  admitted 
a  maximum  mercurial  thermometer  about  6  inches  in  length,  gradu¬ 


ated  in  single  degrees  from  100  to  200°.  When  a  test  was 
to  be  made,  the  thermometer  wras  carefully  slipped  into  the  small 
pipe,  which  was  then  closed  by  a  screw-cap.  Valves  were  so  arranged 
that  the  thermometer  pipe  could  be  surrounded  by  steam  under  full 
pressure  or  steam  discharging  at  any  lower  pressure  down  to  that  of 
the  atmosphere.  Three  thermometers,  made  by  the  Taylor  Instru¬ 
ment  Companies  of  Rochester,  were  used  in  the  measurements  and, 
as  the  table  shows,  there  was  no  systematic  difference  in  their  reading. 
One  of  them,  No.  1,  was  afterward  carefully  calibrated,  and  the  errors 
in  reading  were  found  not  to  be  greater  than  =+=0.1°.  In  making  a 
measurement  the  thermometer  was  left  in  the  pipe  usually  for  15 
minutes,  then  withdrawn  and  read  as  quickly  as  possible  with  a 
reading  glass. 

The  accidental  temperature  errors  from  all  sources  may  be  judged 
by  comparing  the  measurements  made  in  the  same  well  on  the  same 
date,  as  the  latter  represent  duplicate  determinations  made  within  an 


60 


hour.  That  the  differences  are  not  entirely  due  to  errors  of  measure¬ 
ment  is  obvious  from  the  results  in  Well  No.  1  which  remain  unac¬ 
counted  for,  but  they  are  probably  due  chiefly  to  delays  in  with¬ 
drawing  the  thermometer  and  a  consequent  shortening  of  the  mercury 
column  to  which  a  200° -maximum  thermometer  is  prone.  Except 


Table  7. — Measured  temperatures  and  pressures  in  the  Steam  Wells  at  The  Geysers, 
Sonoma  County,  California.  Pressure  and  temperature  taken  at  the  top.  Wells 
closed. 


Place 

Date 

Time 
of  test 
min. 

No.  of 
thermo¬ 
meter 

Temp, 
in  C°. 

Pressure 
in  lbs.  per 
sq.  in. 

p  + 1  at 
(13.81bs.) 

=  p' 

p"  * 

P'-P" 

1925 

Well  1 

June  20 

15 

2 

122.0 

62 

75.8 

30.7 

45.1 

U 

1 

143.8 

62 

75.8 

58.3 

17.5 

21 

U 

2 

148.7 

62 

75. 8 

66.6 

9.2 

26 

U 

1 

154.0 

62 

75.8 

76.7 

0.9- 

27 

U 

3 

154.2 

65 

/  8 . 8 

77.1 

1.7 

Well  2 

June  20 

15 

3 

153.0 

60 

73.8 

74.7 

0.9- 

U 

3 

153.2 

60 

73.8 

75.1 

1.3- 

21 

U 

1 

153.0 

60 

73.8 

74.7 

0.9- 

26 

U 

3 

154.0 

60 

73.8 

76.7 

2.9- 

27 

U 

2 

153.1 

63 

76.8 

74.9 

1.9 

Well  4 

June  17 

15 

1 

98-99 

0 

13.8 

13.8 

0 

18 

U 

110  max. 

98.5  &  99 

0 

13.8 

13.8 

0 

19 

U 

1 

166.0 

62.5 

76.3 

104.1 

27.8- 

a 

2 

166.2 

62.5 

76.3 

104.6 

28.3- 

20 

20 

2 

164.0 

62 

75.8 

99.1 

23.3- 

U 

1 

162.0 

62 

75.8 

94.3 

18.5- 

21 

25 

3 

164.8 

87.5 

101.3 

101.1 

0.2 

26 

15 

2 

167.5 

95.5 

109.3 

108.0 

1.3 

27 

« 

1 

167.2 

95.5 

109.3 

107.2 

2.1 

Well  5' 

June  11 

169.0 

50 

63.8 

112 

48.2- 

15 

1 

181 . 3 

138 

151.8 

149.7 

2.1 

16 

15 

2 

184.0 

145 

158.8 

159.2 

0.4- 

17 

U 

2 

185.0 

152 

165.8 

162.8 

3.0 

18 

U 

1 

186.0 

159 

172.8 

166.5 

6.3 

u 

o 

186.7 

159 

172.8 

169.1 

3.7 

19 

a 

2 

188.0 

167.5 

180.5 

174.0 

6.5 

u 

3 

188.6 

167.5 

180.5 

176.3 

4.2 

u 

1 

188.0 

167.5 

180.5 

174.0 

6.5 

20 

20 

3 

189.2 

169 

182.8 

178.7 

4.1 

21 

15 

1 

190  0 

169 

1S2.8 

181.8 

1.0 

26 

U 

1 

172.0 

102 

115.8 

120.4 

4.6- 

27 

U 

2 

189.0 

180  + 

193.8 

177.9 

15.9 

Well  6 

June  15 

178  5 

116 

129.8 

140.4 

10.6- 

16 

15 

1 

181.0 

116 

129.8 

148.7 

18.9- 

17 

a 

2 

181.0 

116 

129.8 

148.7 

18.9- 

18 

a 

o 

181.0 

116 

129.8 

148.7 

18.9- 

u 

1 

180.0 

116 

129.8 

145.3 

15.5  — 

19 

u 

3 

181.0 

116 

129.8 

148.7 

18.9- 

u 

1 

180.5 

116 

129.8 

147.0 

17.2- 

26 

u 

3 

181.0 

126 

139.8 

148.7 

8.9- 

26 

u 

2 

180.5 

126 

139 . 8 

147.0 

7.2- 

27 

a 

1 

180.0 

123 

136.8 

145.3 

8.5- 

*  p,r  —  the  pressure  of  saturated  steam  in  lbs.  per  sq.  in.  at  the  temperature  read. 


the  duplicates  in  Well  No.  1,  the  differences  are:  0.2°,  0.2°,  2.0°.  0.7°, 
0°,  0.6°,  1.0°,  0.5° — average  about  0.7°  C. 

Pressures  were  measured  with  a  Bourdon  gage,  which  from  time  to 


61 


time  was  compared  with  a  standard.  The  gages  were  temporarily 
screwed  on  to  a  %-inch  pipe  attached  to  the  large  valve  body  and 
controlled  by  a  small  needle-valve.  The  gage  was  never  left  attached 
to  the  pipe  and  was  connected  to  it  only  after  cold  water  had  been 
poured  in.  The  pressures  in  all  the  closed  wells  were  taken  each 
morning  by  li.  B.  Kidd,  usually  about  the  same  time  the  temperatures 
were  read,  but  occasionally  12  hours  earlier  if  the  pressure  had  been 
found  to  be  virtually  constant  for  some  time. 

The  first  fact  of  interest  which  arrests  the  attention  when  table  7 
is  inspected  is  that  in  all  but  one  of  the  wells,  No.  6,  the  pressures  and 
temperatures  eventually  approximate  to  those  of  saturated  steam. 
Since  the  pressure  of  saturated  steam  within  the  temperature  range 
of  these  wells  (154°  to  190°  C.)  varies  from  2  to  4  pounds  per  square 
inch  for  every  degree  Centigrade,  the  final  agreement  appears  satis¬ 
factory.  Well  No.  6  developed  a  pressure  of  240  pounds  not  long 
after  it  was  first  closed.  Fearing  that  steam  under  pressures  of  this 
magnitude  would  force  its  way  outside  the  casing  and  ruin  the  well, 
the  engineer  gave  orders  to  keep  it  open,  and  during  the  several  weeks 
of  our  stay  at  The  Geysers  it  was  discharging  almost  constantly 
through  a  4-inch  outlet  pipe.  Probably  it  is  this  circumstance  that 
is  responsible  for  the  wider  variations  between  p'  (the  total  pressure 
in  the  well)  and  p"  (the  pressure  of  saturated  steam  at  the  tempera¬ 
ture  read)  throughout  the  time  of  the  tests  than  we  find  in  the 
other  wells. 

When  the  figures  in  table  7  are  examined  in  detail,  it  will  be  found 
that  in  Well  2  pressures  and  temperatures  corresponded  pretty  closely 
from  the  first  with  those  of  saturated  steam,  the  average  deviation  in 
pressure  amounting  to  1.6  per  cent  of  the  latter.  All  but  one  of  the 
differences — the  last — are  negative. 

In  Well  1  the  pressure  remained  nearly  constant  while  the  tem¬ 
perature  slowly  rose,  finally  reaching  a  point  where  the  pressure 
approximated  to  that  of  saturated  steam  within  1.7  per  cent. 

After  Well  4  was  closed  the  pressure  lagged  for  several  days,  but 
during  the  last  three  the  pressure  deviated  from  that  of  saturated 
steam  by  an  average  difference  of  1.2  per  cent  only. 

Similar  to  Well  4  was  the  behavior  of  Well  5;  there  was  a  high 
negative  difference  in  pressure  at  first,  falling  after  one  day  to  an 
average  of  3.8  per  cent  for  a  period  of  ten  days  and  reaching  on  June 
21  a  limit  of  0.6  per  cent.  On  the  following  recorded  date,  June  26, 
the  well  being  partially  open,  both  temperature  and  pressure  had 
fallen  markedly.  Most  of  the  differences  here  are  positive. 

The  history  of  No.  6  differs  from  that  of  all  the  other  wells  in  that 
it  was  discharging  throughout  the  time  of  the  tests,  and  here  the 
pressure  was  below  that  of  saturated  steam  in  every  test,  much  lower 
during  the  first  seven  days  and  on  the  average  5.5  per  cent  lower 


during  the  last  three.  All  the  differences  are  negative.  As  the  nega¬ 
tive  differences  signify  that  the  pressure  read  was  lower  than  that  of 
saturated  steam  for  the  recorded  temperature,  the  steam  must  be 
superheated  wherever  such  differences  are  found.  Immediately  after 
the  wells  are  closed,  the  deviations  are  always  in  this  direction.  Wells 
1  and  2  were  generally  kept  closed  during  the  summer  of  1925  and 
they  probably  had  not  been  recently  opened.  This  seems  to  mean 
that  the  steam  as  it  rises  from  the  depths  is  superheated  and  becomes 
saturated  only  after  it  has  stood  under  pressure  in  the  wells — prob¬ 
ably  because  of  the  condensation  of  a  portion  of  the  steam.  Other 
observations  confirm  the  truth  of  this  hypothesis.  In  the  record  of  a 
day's  visit  to  The  Geysers  in  1922  when  the  first  well  (No.  1)  had 
reached  a  depth  of  150  feet,  we  find  that  the  temperature  3  feet  down 
was  109°  C. ;  the  true  temperature  was  probably  higher,  for  the 
thermometer,  graduated  to  only  110°  C.,  was  left  in  but  a  moment. 
This  was  not  a  sporadic  instance;  a  similar  observation  was  made  in 
1924  at  the  top  of  Well  3  (p.  83),  then  100  feet  in  depth,  when  the 
temperature  9  inches  below  the  top  of  the  casing  read  111°  C.1  When 
the  evidence  is  taken  in  its  entirety  the  steam  of  Well  1,  like  all  the 
rest,  appears  also  to  be  originally  superheated. 

The  final  differences  in  pressure  in  the  closed  wells,  as  previously 
remarked,  are  invariably  positive.  Though  too  small  to  be  stressed, 
they  are  reasonably  accounted  for  both  by  the  fact  that  the  tempera¬ 
ture  readings  are  probably  all  a  trifle  low  (p.  60)  and  by  the  fact  that 
the  steam  is  accompanied  by  small  amounts  of  gas  which  would 
naturally  raise  the  pressure  above  that  of  saturated  steam. 

Some  details  of  the  tests  are  still  puzzling;  the  behavior  of  Well  4 
when  discharging  at  atmospheric  pressure  and  the  behavior  of  Well  1 
in  the  beginning  are  anomalous.  A  system  of  piping  with  less  metal 
exposed  at  the  surface,  less  horizontal  pipe  especially,  would  no  doubt 
have  been  an  advantage,  and  more  tests  in  more  wells  and  under  a 
wider  range  of  conditions  would  certainly  have  been  helpful.  Still, 
the  facts  as  they  stand  show  clearly  that  if  the  wells  are  kept  closed 
the  steam  finally  reaches  a  pressure  which  corresponds  to  that  of 
saturated  steam  at  the  temperature  read  at  the  top  of  the  well,  and 
what  is  of  greater  interest  to  the  geologist,  they  show  that  the  steam 
is  originally  superheated.  Mr.  Galloway  says  (personal  letter  of 
March  6,  1926)  of  some  later  temperature  measurements  of  his  own: 

“The  temperatures,  which  I  took  of  the  steam- wells  at  The  Geysers,  were  taken 
when  the  wells  were  discharging.  At  that  time  the  temperatures  seemed  to  correspond 
closely  to  that  of  saturated  steam.  Some  later  tests  made  this  year  indicate  from  15° 
to  25°  of  superheat.” 

1  Later  temperature  measurements  at  the  top  of  the  deeper  wells,  when  the  valves 
were  wide  open,  gave  much  higher  readings  (pp.  83  and  84). 


63 


CHARACTERISTICS  OF  SUBTERRANEAN  STEAM  IN  OTHER  LOCALITIES 


But  this  is  not  the  full  extent  of  our  knowledge  concerning  sub¬ 
terranean  steam;  many  observations  and  measurements  of  its  tem¬ 
perature  and  pressure  in  other  places  are  also  on  record.  De  Stefani1 
states  that  the  pressure  of  the  steam  in  the  older  and  shallower 
Tuscan  wells,  as  measured  by  a  manometer,  ranges  from  1.5  to  1.75 
atmospheres  as  a  rule,  but  at  a  maximum  reaches  as  high  as  9 
atmospheres.  Nasini,2  commenting  on  these  measurements,  says  that 
the  pressures  in  the  stronger  wells,  being  difficult  to  measure,  were 
merely  estimated  from  the  temperature  on  the  assumption  that  the 
steam  was  saturated.  When  later  on  the  pressures  came  to  be 
actually  measured,  wide  discrepancies  were  revealed,  as  may  be  seen 
from  the  following  data: 


Fumarole 

t 

p  (found) 

p  cal.  from  t 

Foro  di  piazzi  anna . 

162° 

3.0  at.  absol. 

6.4  at. 

Foro  forte . 

162 

2.5 

6.4 

Foro  della  Venella . 

150 

4.0 

4.7 

The  figures  show  that  the  steam  is  superheated  as  Nasini  pointed 
out.  The  steam  from  these  older  wells  was  utilized  for  the  concen¬ 
tration  of  solutions  in  the  preparation  of  boric  acid  and  other 
chemicals.  Since  then  the  new  Tuscan  power  wells  have  been  devel¬ 
oped  and  measurements  of  the  temperature  and  pressure  in  them, 
according  to  recent  statements  of  Ginori  Conti,3  confirm  the  earlier 
assertions  of  Nasini.  Most  of  the  pressure  measurements  at  Lar- 
clerello  appear  to  have  been  made  when  the  steam  was  discharging; 
whether  any  of  them  are  comparable  to  those  made  at  The  Geysers 
where  observations  were  made  on  wells  which  had  been  kept  closed 
for  a  week  or  more,  the  statements  are  not  sufficiently  detailed  to 
make  clear. 

These  are  the  only  places  in  the  world  where  the  pressures  of 
natural  steam  are  known  to  have  been  actually  measured,  but  obser¬ 
vations  have  been  made  elsewhere  which,  though  less  direct,  are 
almost  equally  convincing.  Many  fumaroles  in  the  Katmai  region, 
Alaska,  must  emit  superheated  steam,  for  in  1919  lead  and  even  zinc 
melted  in  the  hottest  ones4  within  a  few  feet  of  the  surface  and  less 
frequently  within  a  few  inches,  yet  the  steam  was  often  escaping 

1  I  soffioni  horaciferi  della  Tuscana.  Memorie  della  Society  Geografica  Italiana,  VI,  pt.  2, 
p.  410,  1897. 

2  I  soffioni  horaciferi,  e  la  industria  dell’  acido  borico  in  Tuscana,  Rome,  1907. 

3  The  natural  steam  power  plant  of  Larderello,  page  8,  Firenze,  1924. 

4  The  maximum  temperature  was  045°  C.,  while  13  other  temperatures  were  above  the  critical 
temperature  of  water  where  the  term  “saturated  steam”  ceases  to  have  any  meaning.  (Allen 
and  Zies.) 


64 


rather  quietly,  sometimes  under  considerable  pressure  but  never  with 
the  manifestations  of  potential  pressure  (noise  and  velocity)  charac¬ 
teristic  of  much  cooler  fumaroles  in  that  locality. 

Fumaroles  have  been  found  by  the  authors  in  the  Lassen  National 
Park  and  other  places  emitting  steam  at  temperatures  ranging  from 
5°  C.  to  50°  C.  above  the  boiling  point  of  water  for  the  locality. 
While  the  noise  of  escaping  steam  was  always  indicative  of  excess 
pressure  inside  the  vent,  the  temperatures  were  taken  so  close  to  the 
surface  (usually  within  a  foot  or  two,  sometimes  much  less)  that  it 
is  incredible  that  the  steam  was  not  superheated,  at  least  in  the 
hottest  fumaroles.  True,  many  fumaroles  at  Katmai  and  elsewhere 
emit  steam  at  about  the  temperature  of  boiling  water  for  the  atmos¬ 
pheric  pressure,  a  phenomenon  readily  explained  on  the  assumption 
that  they  are  affected  by  ground  water,  but  the  facts  so  far  as  they 
go  indicate  that  the  steam  is  originally  superheated. 

NON-CONDENSABLE  GASES  IN  THE  STEAM 

Certain  gases  accompany  the  natural  steam  from  the  wells  of  Cali¬ 
fornia,  as  one  discovers  when  the  steam  is  condensed  under  proper 
conditions.  To  get  a  sample  of  the  gases,  the  outlet  pipe  of  the  well 
to  be  tested  was  tapped  with  a  drill,  generally  close  to  the  casing,  and 
a  %-inch  pipe  carrying  a  small  needle- valve  was  then  fitted  into  the 
drill-hole  so  that  a  sample  of  steam  could  be  drawn  off  while  the 
steam  flow  was  under  control.  A  piece  of  quarter-inch  (inside  diam¬ 
eter)  glazed  Berlin  porcelain  tubing,  several  feet  in  length,  was  then 
attached  to  the  outlet  of  the  needle-valve  with  a  heavy-walled  flexible 
rubber  connection  tightly  wired  on,  and  to  the  open  end  of  the  tube 
was  attached  a  short  right-angle  of  glass  with  the  free  end  turned 
upward.  The  latter  was  then  held  down  in  a  bucket  of  water  and  the 
steam  turned  on.  When  the  water  was  boiling-hot  or  nearly  so  a  gas- 
collecting  tube  was  filled  with  it  and  the  gas  was  collected  by  displace¬ 
ment  in  the  usual  way.1 

To  determine  the  amount  of  the  other  gases  which  accompany  the 
steam,  a  suitable  amount  of  the  latter  is  condensed  and  its  volume 
determined  while  the  gases  which  it  contains  are  caught  and  measured. 
For  the  exigencies  of  field  work  it  will  be  obvious  that  advantage  lies 
with  apparatus  of  maximum  simplicity  consistent  with  reasonable 
accuracy.  The  apparatus  used  in  the  present  case  (fig.  28)  consisted 
of  an  air-cooled  tube,  water  condenser  and  metal  aspirator  joined  in 
series.  The  first  was  made  up  of  several  3-foot  lengths  of  quarter- 
inch  glazed  Berlin  porcelain  tubes  all  tightly  connected  together  with 
heavy-walled  flexible  rubber  tubing,  the  whole  joining  the  outlet  of 
the  needle  valve  to  the  condenser.  The  condenser  was  an  ordinary 

1  Day  and  Allen,  op.  cit.,  p.  123. 


Fig.  28 — Field  equipment  for  determining  gases  accompanying  steam  at  Well  No.  2.  1925. 


66 


pyrex  flask  of  700  c.c.  capacity,  with  stopper,  inlet  and  outlet  tubes 
like  a  wash  bottle.  Then  followed  a  pyrex  cylinder  of  125  c.c.  capacity, 
fitted  in  the  same  way  and  joined  to  the  condenser  as  guard.  The 
flask  and  cylinder  were  mounted  on  a  suitable  stand  with  wooden 
base  so  that  either  the  cylinder  or  both  cylinder  and  flask  could  be 
cooled  by  a  dish  of  water.  By  a  small  rubber  tube  several  feet  in 
length  the  cylinder  was  connected  to  the  top  of  the  aspirator  (capacity 
12  liters)  through  a  one-hole  stopper.  To  prevent  any  air  leaking  up 
into  the  outlet  tube  of  the  aspirator  a  quarter-inch  copper  tube  about 
2  feet  in  length  was  connected  to  the  outlet  in  vertical  position.  All 
the  connections  and  the  stopper  of  the  condenser  were  tightly  wired 
(fig.  29). 


Fig.  29 — Sketch  of  apparatus  for  determining  ratio  of  gases  to  steam. 


In  carrying  out  a  determination  the  aspirator  and  its  outlet  were 
filled  with  water,  and  to  insure  condensation  of  the  steam  at  the  start 
a  small  amount  of  water,  about  35  c.c.  in  all,  w^as  poured  into  con¬ 
denser  and  guard  cylinder.  A  one-liter  glass  graduate  (protected  by 
a  special  rubber  casing)  was  then  set  under  the  outlet  of  the  aspirator, 
the  stop-cock  of  the  latter  was  opened  and  steam  cautiously  let  in  by 
the  needle-valve.  The  steam  condenses  in  flask  and  cylinder;  the 
uncondensed  gas  together  with  the  air  in  the  apparatus  passes  on  and 
is  caught  in  the  aspirator,  while  the  water  displaced  in  the  latter 
flows  into  the  graduate.  As  the  graduate  fills,  the  flow  is  stopped  for 
a  moment  while  the  volume  of  water  is  read  and  recorded,  after  which 
the  water  is  thrown  out  and  the  operation  continued.  To  drive  out 
the  soluble  gases  as  far  as  possible  from  the  condensed  steam,  the 


67 


68 


temperature  of  the  water  in  the  condenser  is  permitted  to  reach  about 
70  C.,  while  the  cylinder  is  kept  cool  to  condense  the  vapor.  These 
precautions  apply  chiefly  to  the  carbon  dioxide;  the  hydrogen  sulphide 
and  ammonia  form  only  a  small  percentage  of  the  total  gases  and 
both  are  determined  later  in  separate  tests.  As  to  the  carbon  dioxide, 
the  amount  of  it  dissolved  in  the  water  of  the  guard  cylinder  is  unim¬ 
portant  since  the  volume  of  the  water  is  only  50  c.c.  or  less,  while 
that  of  the  gas  reaches  5  to  10  liters.  Furthermore  the  solution  of 
carbon  dioxide  in  the  water  of  the  aspirator  need  not  be  feared  as  the 
gas  does  not  bubble  through  it  and  remains  in  contact  with  it  but  a 
half  hour.  Even  if  10  per  cent  of  the  carbon  dioxide  were  thus  dis¬ 
solved,  the  total  error  in  the  percentage  of  the  uncondensed  gases 
would,  in  the  most  extreme  case,  amount  to  less  than  0.15  per  cent 
of  the  total  steam  and  gas  mixture. 

The  volume  of  condensed  water,  amounting  to  several  hundred 
cubic  centimeters  was  also  quite  sufficient  to  insure  a  satisfactory 
determination  of  the  steam.  During  a  test,  the  aspirator  was  shielded 
from  sun  and  wind  by  a  large  canvas  sail,  and  a  sensitive  thermometer 
resting  against  the  aspirator  was  read  several  times  in  the  course  of 
each  test  to  determine  the  approximate  temperature  of  the  gas,  while 
the  water  was  kept  as  nearly  as  possible  at  the  temperature  of  the  air. 
Proper  corrections  of  course  were  made  for  air  displaced  by  water  in 
the  condenser  and  for  reduced  pressure  in  the  aspirator.  The  con¬ 
densed  water  was  measured  as  accurately  as  feasible  under  field  con¬ 
ditions  with  the  100  c.c.  graduate. 

The  last  column  in  table  8  gives  the  percentage  by  volume  of  the 
uncondensed  gases  (C02,  N2,  CH4,  etc.)  in  the  mixture  of  gas  and 
steam.  The  results  for  different  wells  vary  from  0.75  per  cent  to  1.95 
per  cent  by  volume,  or  from  1.33  to  3.35  per  cent  by  weight.  The 
amount  is  of  some  importance  industrially  since  steam  turbines  will 
be  used  in  the  generation  of  power,  and  with  them  of  course  the  more 
complete  the  condensation  of  steam,  the  greater  the  power  developed. 
In  this  respect  the  steam  at  The  Geysers  has  the  advantage  over  that 
in  Tuscany,  for  the  latter,  according  to  Na§ini,  contains  from  3  to  5 
per  cent  by  weight  of  non-condensable  gases. 

ANALYSIS  OF  THE  NON-CONDENSABLE  GASES 

Gases  from  steam-wells,  springs  and  fumaroles  were  collected  and 
analyzed  so  that  the  results  might  be  correlated  with  other  data.  A 
method  for  the  collection  of  gases  from  hot  springs  has  already  been 
described  by  the  authors.1  Fumarole  gases  can  be  collected  free  from 
air  only  when  the  flow  of  gas  is  strong.  The  method  adopted  here  was 
air  displacement  combined  with  steam  condensation.  The  apparatus 


1  Day  and  Allen,  p.  123. 


69 


used  was  the  same  which  served  in  the  determination  of  steam  ( p. 
66);  the  gas  tube  open  at  both  ends  was  simply  connected  into  the 
train  between  the  condenser  guard  and  the  aspirator.  Measurements 
were  of  course  dispensed  with.  The  only  fumarole  gas  analyzed  con¬ 
tains  less  nitrogen  than  any  other  gas  sample  (see  table  9)  showing 
clearly  that  air  was  completely  eliminated  in  its  collection. 


Table  9. — Gases  from  wells,  springs,  and  fumaroles  at  The  Geysers,  and  Little  Geysers , 

Sonoma  County,  California. 


Locality 

C02 

02 

CO 

h2 

ch4 

n2+a 

h2s 

Sum 

Well  No.  1 . 

64.40 

none 

none 

14.90 

15.50 

3.60 

1.60 

100.00 

No.  2 . 

61.30 

none 

17.05 

16.45 

3.80 

1.40 

100.00 

No.  4 . 

62.45 

none 

16.65 

15.90 

3.45 

1.60 

100.05 

No.  5 . 

65.10 

none 

none 

14.60 

15.25 

3.20 

1.90 

100.05 

No.  6 . 

65.20 

none 

none 

14 . 65 

15.40 

3.45 

1 . 35 

100.05 

Steamboat  Fumarole . 

67.45 

none 

none 

12.75 

14.30 

2.85 

2.70 

100.05 

Tea-kettle . 

65.35 

none 

none 

14.00 

15 . 65 

3.95 

1.20 

100.15 

Spring  in  Sulphur  Creek. . .  . 

63.45 

none 

14.50 

17.10 

4.00 

1.00 

100.05 

Spring  4  Geyser  Creek . 

Witches’  Cauldron  Upper 

53.35 

none 

none 

18.00 

23.25 

5.45 

0.15 

100.20 

Pool . 

65.25 

none 

none 

13.05 

16.65 

4.10 

1.00 

100.05 

Ink  Spring . 

62.00 

none 

none 

14.60 

18.55 

3.75 

1.25 

100.15 

Spring  3  Little  Geysers  1 . . .  . 

77.30 

0.05 

none 

2.20 

14.15 

6.35 

none 

100.05 

Spring  4  Little  Geysers . 

73.60 

0.10 

none 

1.85 

16.55 

7.90 

none 

100.00 

Spring  5  Little  Geysers . 

75.50 

0.20 

none 

1.75 

12.70 

/9.80 

\0.102 

none 

100.05 

1  Spring  3  is  the  largest  pool  on  the  small  central  plateau,  the  most  active  portion  of  the  area 
(t  =  87.3°).  Springs  4  and  5  are  at  a  somewhat  lower  level,  a  little  southwest  of  the  cabin  and 
about  10  feet  apart.  No.  5  was  filled  with  thin  gray  mud  (t  =  95.9°)  and  No.  4  was  a  shallow 
spring  of  the  “frying-pan”  type  (t  =  71.0°).  The  temperatures  were  taken  at  the  time  the 
gases  were  collected,  June  24,  1926. 

2  Nitrogen  and  argon  separately  determined. 

The  analytical  methods3  applied  to  these  gases  were  the  same  as 
those  used  on  the  gases  from  the  Lassen  National  Park,  with  certain 
modifications  adapted  to  their  peculiar  composition.  The  lead  perox¬ 
ide  method  for  hydrogen  sulphide  was  compared  with  the  iodometric 
method,  which  is  doubtless  the  most  accurate,  though  a  separate 
sample  is  necessary  where  it  is  used.  For  reasons  which  have  been 
discussed,  it  is  still  necessary  to  use  the  lead  peroxide  in  the  analysis 
of  the  other  sample.  Assuming  the  iodometric  method  to  give  exact 
results,  the  determinations  by  the  use  of  the  lead  peroxide  pellet  are 
in  error  by  0.03  per  cent  to  0.28  per  cent,  averaging  0.12  per  cent — 
practically  all  positive. 

When  the  high  percentage  of  combustible  constituents  in  the  gases 
from  The  Geysers  was  discovered,  the  procedure  was  modified  by  the 
introduction  of  another  pipette  holding  an  alkaline  solution  of  col¬ 
loidal  palladium  into  the  train  of  the  apparatus,  a  solution  used  for 
the  absorption  of  hydrogen.  This  excellent  method  of  Paal  and  Hart- 


3  Day  and  Allen,  op.  cit,  p.  124. 


70 


mann1  deserves  high  praise.  Duplicate  determinations  in  our  experi¬ 
ence  generally  agree  exactly,  and  never  vary  more  than  0.05  per  cent. 
It  greatly  simplifies  the  problem  of  the  determination  of  the  hydro¬ 
carbons;  its  only  drawback  seemingly  is  that  it  works  slowly.  An 
hour  was  allowed  in  the  absorption  of  these  comparatively  high 
percentages. 

Ethane  has  been  reported  in  the  gases  from  the  steam-wells,  but 
the  close  agreement,  when  the  hydrogen  is  first  removed,  between  the 
combustion  data  on  the  one  hand  and  the  amount  of  gas  after  the 
removal  of  hydrogen,  less  the  nitrogen,  on  the  other,  proves  beyond 
question  that  there  is  in  none  of  these  gases  any  appreciable  amount 
of  any  hydrocarbon  besides  methane.  For  the  complete  combustion 
of  methane  the  following  details  were  found  useful.  The  residue 
which  contains  the  hydrocarbons  having  first  been  driven  into  the 
potash  pipette,  pure  electrolytic  oxygen  in  amounts  varying  from  35 
c.c.  to  50  c.c.  is  drawn  into  the  burette  and  measured,  then  driven  over 
into  the  combustion  pipette.  When  the  wire  in  the  latter  has  been 
heated  to  incandescence,  the  combustible  gas  is  passed  slowly  in  and 
afterward  drawn  back  and  forth  several  times.  The  contraction  is 
then  measured  and  the  carbon  dioxide  absorbed.  Further  combustion 
may  then  be  effected  with  the  residue.  When  the  contraction  has 
again  been  measured  and  the  carbon  dioxide  absorbed  as  before,  about 
half  the  residue  is  left  in  the  combustion  pipette  while  the  remaining 
portion  is  measured.  The  latter  is  then  entirely  deprived  of  its 
oxygen  and  the  nitrogenous  residue  is  used  to  displace  all  the  methane 
in  the  capillaries,  which  finally  is  brought  to  combustion  with  the 
remaining  oxygen. 

At  last  the  oxygen  is  entirely  removed,  and  from  the  nitrogen  left 
is  subtracted  any  nitrogen  which  the  original  oxygen  may  have 
contained. 

COMPOSITION  OF  THE  GASES 

These  gases  are  sharply  distinguished  from  those  of  Lassen  National 
Park  by  their  lower  percentage  of  carbon  dioxide  (though  this  gas  is 
still  present  in  large  excess)  and  by  their  unusually  high  percentages 
of  hydrogen  and  marsh  gas  (table  9).  Many  springs  elsewhere  are 
characterized  by  very  large  amounts  of  methane  in  their  gases  (almost 
certainly  of  secondary  origin)  and  there  are  some  hot-spring  gases, 
notably  many  from  Iceland,  which  are  high  in  hydrogen,  but  rarely 
do  both  constituents  occur  together  in  large  amounts.2 

Considering  together  the  gases  from  the  steam-wells  and  from  the 
Steamboat  Fumarole  as  least  modified  by  surface  influences,  we  find 
(table  9)  that  the  carbon  dioxide  varies  from  61.3  per  cent  to  67.4 
per  cent,  averaging  64.3  per  cent.  Hydrogen  varies  from  12.75  per 

1  Ber.  Chem.  Gesel.,  43,  243,  1910. 

2  Jour.  Franklin  Inst.,  193,  p.  68,  1922. 


71 


cent  to  17.05,  with  a  mean  of  15.1  per  cent.  Methane  varies  from 
14.30  per  cent  to  16.45  per  cent,  with  a  mean  of  15.6  per  cent,  and 
nitrogen  varies  from  2.85  to  3.80  per  cent,  averaging  3.4  per  cent. 
Oxygen  and  carbon  monoxide  within  the  limits  of  error  are  absent. 

The  smaller  amounts  of  hydrogen  sulphide  as  compared  to  those 
determined  by  absorption  in  the  field  and  recorded  in  the  next  section 
of  this  paper  are  to  be  attributed  to  the  method  of  collection  which, 
though  sound  in  principle,  proved  faulty  in  practice.  The  water  over 
which  they  were  collected  turned  dark  in  the  process  and  presumably 
contained  iron  which  retained  a  part  of  the  sulphur.1  The  results 
obtained  by  absorption  of  this  gas  with  caustic  soda  are  considerably 
higher  and  doubtless  more  accurate  (p.  73).  On  the  other  hand  the 
amounts  of  the  hydrogen  sulphide  found  in  the  spring  gases  pre¬ 
sumably  represent  the  proportions  which  actually  escape  from  the 
springs.  Abundant  evidence  points  to  the  oxidation  of  much  of  the 
sulphur  by  air  and  a  part  of  the  residual  nitrogen  from  this  air  is 
doubtless  found  with  the  gases,  as  the  quantity  of  nitrogen  in  the 
spring  gases  is  almost  always  higher  than  it  is  in  the  steam-wells.  In 
the  gases  of  The  Little  Geysers  the  relatively  high  percentages  of 
nitrogen  are  quite  in  accord  with  the  absence  of  hydrogen  sulphide. 
For  the  very  much  lower  percentages  of  hydrogen  in  The  Little 
Geysers  we  have  as  yet  no  explanation. 

Since  certain  constituents,  notably  water  and  carbon  dioxide,  are 
invariably  present,  we  infer  that  they  are  magmatic,  though  even 
these  may  be  augmented  by  further  additions  from  secondary  sources. 
Gases  from  fumaroles,  hot  springs  and  craters  are  liable  to  contain 
extraneous  matter  derived  from  the  terranes  they  traverse  just  as 
igneous  rocks  may  contain  secondary  material  with  which  the  original 
substance  has  been  melted  and  incorporated.  On  the  other  hand  the 
gases  directly  derived  from  igneous  rocks  are  probably  only  a  fraction 
of  the  original  quantity  and  do  not  necessarily  represent  the  original 
proportions,  indeed,  some  constituents  may  have  vanished  entirely. 

It  would  be  very  interesting  if  we  could  trace  the  gases,  magmatic 
or  otherwise,  to  their  original  sources.  It  is  not  inconceivable 
that  we  may  eventually  be  able  to  predict  from  the  composition  of 
the  volcanic  gases  which  arise  in  a  given  locality  the  nature  of  the 
inaccessible  magma  which  lies  beneath.  In  any  event  we  need  to 
know  the  quantities  of  the  chemically  active  gases  carbon  dioxide, 
the  sulphur  gases,  and  the  halogens,  when  present,  whether  they  are 
magmatic  or  not,  since  they  play  such  an  important  part  in  the  modi¬ 
fication  of  the  superficial  strata  through  which  they  pass,  in  the 
formation  of  mineral  waters  and  in  the  determination  of  salient 
features  of  the  landscape. 

1  The  significance  of  this  behavior  was  not  realized  at  the  time;  the  water  taken 
was  thought  to  be  pure  enough  for  the  purpose. 


72 


SOLUBLE  GASES 

In  the  determination  of  the  “soluble”  gases  which  accompany  the 
natural  steam  the  apparatus  described  in  the  preceding  section  was 
employed. 

HYDROGEN'  SULPHIDE 

Hydrogen  sulphide  in  many  hot-spring  and  fumarole  regions  is  the 
most  active  agent  in  rock  decomposition,  yet  the  amounts  of  it  have 
been  carefully  determined  in  only  a  few  localities.  This  gas  will  also 
have  to  be  taken  into  account  in  the  construction  of  a  power  plant, 
owing  to  its  corrosive  action  on  metals — whether  accompanied  by 
oxygen  or  not.  It  may  be  noted  here  that  the  determination  of  “non¬ 
condensable”  gas  doubtless  includes  some  hydrogen  sulphide,  but 
since  the  total  amount  of  the  latter  is  only  0.03  per  cent  of  all  the 
gases  including  steam,  the  error  is  negligible.  In  the  determination 
of  hydrogen  sulphide  we  measure  the  amount  absorbed  when  a 
measured  amount  of  steam  is  condensed.  About  50  c.c.  of  solution 
containing  10  grams  pure  caustic  soda  is  used  for  absorption,  most  of 
it  being  poured  into  the  condenser,  but  a  little  reserved  for  the  guard 
cylinder.  Distilled  water  is  required  for  the  solution  and  it  is  needed 
also  to  wash  out  the  entire  apparatus  at  the  beginning  of  each  test. 
The  flow  of  gas  is  carefully  controlled  by  the  needle-valve  so  that 
hydrogen  sulphide  will  all  be  absorbed  by  the  soda  and  only  a  neg¬ 
ligible  amount  of  water  vapor  will  escape.  Here  as  before,  the  guard 
cylinder  especially  should  be  kept  cool.  At  the  end  of  the  experiment 
the  total  volume  of  the  solution  is  measured  and  the  temperature 
taken  so  that  the  weight  of  condensed  steam  can  be  found.  The  solu¬ 
tion  is  poured  into  a  clean  bottle  and  to  it  are  added  the  washings 
from  condenser,  cylinder  and  finally  the  cooling  tube  which  is  detached 
for  the  purpose.  Before  shipment  the  solution  is  boiled  thoroughly 
with  an  excess  of  “dioxogen”  to  oxidize  all  the  sulphur  to  sulphate, 
after  which  it  is  cooled,  acidulated  with  hydrochloric  acid  to  keep  the 
stopper  from  sticking,  and  finally  washed  back  into  the  bottle  and 
sealed.  On  our  return  to  the  laboratory  in  Washington  the  whole 
solution  was  diluted  to  1  liter  and  determinations  made  of  the  sulphur 
in  aliquot  parts.  To  avoid  the  serious  error  involved  in  precipitating 
barium  sulphate  from  a  solution  relatively  high  in  sodium  chloride, 
each  portion  was  evaporated  to  dryness  on  the  water-bath,  a  little 
water  added  and  the  sodium  chloride  precipitated  with  an  excess  of 
concentrated  hydrochloric  acid  solution.  Finally  the  precipitated  salt 
was  filtered  through  a  Gooch  crucible  and  washed  with  successive 
small  portions  of  concentrated  hydrochloric  acid.  Several  of  the  salt 
residues  were  dissolved  separately  and  tested  for  sulphate.  Less  than 
a  milligram  of  barium  sulphate  as  a  rule  was  obtained.  The  average 
amount  is  used  in  correction.  After  the  hydrochloric  acid  was  evapo- 


Table  10. — Volume  percentages  oj  hydrogen  sulphide  accompanying  steam  in  steam-wells  and  fumaroles  at  The  Geysers,  Sonoma  County 

California. 


73 


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74 


rated  from  the  main  solution  the  sulphate  was  determined  as  usual. 
In  table  10  are  recorded  the  essential  field  and  laboratory  data,  and 
the  hydrogen  sulphide  is  computed  in  grams  per  kilo  of  steam  and 
also  in  volume  percentage,  that  is,  the  volume  of  gas  at  the  tempera¬ 
ture  and  pressure  of  boiling  water  at  the  time  and  place,  divided  by 
the  total  volume  of  both  gas  and  steam  under  the  same  conditions.1 
The  natural  fumaroles  will  be  seen  to  contain  similar  amounts  of 
hydrogen  sulphide  as  the  steam-wells. 

AMMONIA 

Inasmuch  as  ammonium  is  more  abundant  in  the  springs  than  are 
any  of  the  metals,  it  was  considered  worth  while  to  determine  it  in  the 
emanation  from  the  wells  and  fumaroles.  The  same  apparatus  was 
employed  as  that  used  for  hydrogen  sulphide.  Instead  of  the  caustic 
soda  a  measured  volume  of  dilute  sulphuric  acid  was  used  as  the 
absorbent  and  to  it  a  little  methyl  orange  was  added  to  indicate 
whether  the  amount  of  acid  was  sufficient  for  the  safe  retention  of 
the  ammonia.  The  data  required  of  course  were  the  amount  of 
steam  condensed  and  the  amount  of  ammonia  absorbed  at  the  same 
time.  Thus  we  obtain  the  weight  of  ammonia  associated  with  a  kilo¬ 
gram  of  steam.  In  computing  the  volume  percentage2  it  will  be 
found  that  the  neglect  of  the  “insoluble’1  or  uncondensed  gases  affects 
the  result  not  more  than  one  unit  in  the  third  decimal  place  (0.001 
per  cent).  To  determine  the  ammonia  the  contents  of  the  condenser 
and  guard  cylinder  and  the  washings  from  the  whole  apparatus  were 
poured  into  a  bottle,  sealed  and  shipped  home.  The  solution  was 
eventually  diluted  to  one  liter  and  aliquot  parts  were  distilled  with 
soda,  the  ammonia  caught  in  a  measured  amount  of  standard  acid 
and  titrated  with  standard  alkali.  Table  11  shows  that  the  results  are 
reasonably  uniform  over  the  area  and  of  the  same  order  of  magnitude 
in  the  natural  fumaroles  as  in  the  steam  wells. 

The  question  of  combination  in  wells  and  fumaroles  of  the  gases, 
ammonia  and  hydrogen  sulphide,  can  be  answered  from  the  experi¬ 
ments  of  Isambert,3  who  proved  years  ago  that  a  mixture  of  the  two 
gases  obeys  the  gas  laws  at  temperatures  between  35°  and  40°  C.  and 

/  p  v 

pressures  varying  from  720  mm.  to  1030  mm.  I  -p  0  =  1.007  to  1.008 

just  as  a  mechanical  mixture  of  the  gases  ought  to  do,  whereas  if  com¬ 
bination  occurred  a  contraction  out  of  proportion  to  pressure  would 
have  resulted.  He  also  found  that  when  the  gases  were  brought  into 
contact  at  various  pressures  and  temperatures  between  27°  and  132°  C. 

1  The  expansion  of  both  steam  and  gas  from  the  boiling  point  of  water  to  the  temperature  of 
well  or  fumarole  was  of  course  assumed  to  be  the  same. 

2  The  computation  assumes  that  ammonia  gas  and  steam  when  mixed  at  high  temperatures 
undergo  no  contraction.  This  may  not  be  strictly  correct. 

3  Comp,  rend.,  95,  p.  1355,  1882. 


Table  12. — Amounts  of  gases  in  steam  from  steam-wells  at  The  Geysers,  Sonoma  County,  California. 


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there  was  no  heat  evolved  unless  there  was  condensation,  in  which 
case  the  heat  effect  was  the  same  as  the  heat  of  formation  of  the 
salt  from  its  gaseous  components.  The  dissociation  of  the  salt  is 
therefore  practically  complete  under  conditions  far  less  favorable 
than  those  of  the  steam  wells  and  fumaroles  where  the  temperatures 
are  much  higher  and  the  partial  pressures  of  the  components, 
ammonia  and  hydrogen  sulphide,  insignificant. 

The  components  of  ammonium  acid  carbonate  (NH4HC03)  are 
also  found  in  the  steam.  The  dissociation  of  this  salt  has  not,  ap¬ 
parently,  been  worked  out,  but  like  other  ammonium  salts  it  is  known 
to  be  greatly  affected  by  water  vapor,  and  despite  the  more  favorable 
partial  pressures  than  in  the  case  just  considered,  it  is  doubtful 
whether  any  of  the  compound  exists  at  these  relatively  high  tem¬ 
peratures. 

BORIC  ACID 

The  steam  from  two  of  the  wells  and  from  two  natural  fumaroles 
was  tested  for  boric  acid  by  the  method  used  for  hydrogen  sulphide; 
a  measured  amount  of  steam  was  condensed  while  the  boric  acid  asso¬ 
ciated  with  it  was  absorbed  by  caustic  soda.  The  solution  was  sealed 
and  shipped  to  Washington  where  subsequently  the  boric  acid  in  an 
aliquot  part  was  determined.  All  four  samples  were  thus  examined 
but  unfortunately  the  notebook  containing  the  amount  of  steam  con¬ 
densed  in  each  case  was  lost.  It  is  therefore  impossible  to  give  exact 
figures,  but  it  is  certain  that  the  amount  of  boric  acid  in  these  samples 
could  not  have  been  more  than  20  to  40  parts  per  million  by  weight. 

SUMMARY  OF  GAS  ANALYSES 

For  convenience  in  comparison,  the  percentages  of  non-condensable 
gases  as  well  as  the  percentages  of  the  highly  soluble  constituents  in 
the  various  natural  mixtures  of  steam  and  gas  are  summarized  in 
table  12.  By  combining  these  data  with  those  of  table  9  we  get  the 
complete  analyses  of  all  but  one1  of  the  gases  from  wells  and  fumaroles. 
The  results  are  expressed  in  table  13. 


Table  13. — Complete  analyses  of  several  volcanic  gases  from  The  Geysers,  California. 

Computed 2  from  the  data  in  tables  9  and  12. 


Place 

HcO 

C02 

H, 

ch4 

n2+a 

h2s 

nh3 

Sum 

Well  1 

98  045 

1  242 

0  287 

0  299 

0  069 

0  033 

0 . 025 
.023 

100  000 

o 

. 

98 . 686 

.  777 

.216 

.208 

.048 

.042 

100.000 

5 . 

98.869 

.716 

.160 

.167 

.035 

.035 

.018 

100.000 

6 . 

98.946 

.661 

.148 

.156 

.034 

.037 

.018 

100.000 

Steamboat  Fumarole. 

99 . 202 

.520 

.098 

.110 

.022 

.029 

.019 

100.000 

1  The  sulphur  determination  in  the  gas  from  Well  4  was  vitiated  by  some  coarse  error. 

2  These  figures  are  given  to  thousandths  of  a  per  cent  regardless  of  experimental  error  in  the 
principal  constituents,  the  better  to  express  the  relationship  to  the  lower  constituents. 


COMPARISON  OF  AMOUNTS  OF  SULPHUR  AND  AMMONIA  IN  GASES  AND 

SPRINGS 


If  we  admit  that  there  is  no  other  source  of  sulphur  and  ammonia 
in  the  spring  waters  than  the  volcanic  gases,  a  fact  which  seems  well 
established,  a  comparison  of  the  composition  of  gases  and  waters  may 
lead  to  some  interesting  inferences.  In  table  14  the  amounts  of 
ammonium  and  the  sulphate  radical  in  the  spring  waters  are  copied 
from  table  3,  and  from  them  the  equivalent  amounts  of  ammonia  and 
hydrogen  sulphide  in  terms  of  volume  and  weight  per  kilo  (approxi¬ 
mately)  of  water  are  computed.  Among  the  acid  springs  are  two,  the 
“ Arsenic"  and  the  “Lemonade”  springs,  which  carry  amounts  of 
ammonia  and  sulphur  similar  to  those  in  the  gases.  All  the  rest  of 
the  acid  springs  contain  much  more.  Among  the  alkaline  springs,  the 
Ink  Spring1  is  exceptional  in  containing  as  much  sulphur  per  unit 
weight  of  water  as  the  original  gases  and  still  more  ammonia,  but  all 
the  other  alkaline  springs  show  a  marked  diminution  in  both  con¬ 
stituents.  Despite  the  rather  limited  number  of  figures  at  our  dis¬ 
posal,  the  increase  of  sulphur  and  ammonia  in  the  acid  springs  and 
the  decrease  in  the  alkaline  springs  is  a  fact  too  striking  and  too  con¬ 
sistent  to  be  without  significance.  It  seems  to  denote  concentration 
on  the  one  hand  and  dilution  on  the  other.2 


PROCESSES  OF  SPRING  FORMATION 


When  we  attempt,  on  the  basis  of  evidence,  to  picture  to  ourselves 
the  changes  physical  and  chemical,  which  the  ground  water  and  the 
gases  pass  through  from  the  time  the  latter  reach  the  upper  strata  of 
the  ground  till  both  find  an  outlet  in  the  basin  of  some  spring,  we  see 
first  the  condensation  of  a  part  of  the  steam  and  a  retention  of  a 
portion  of  the  gases  in  the  zone  of  ground  water  which  extends  over 
the  area  as  a  mantle  of  uneven  thickness,  but  on  the  whole  quite  thin, 
reaching  in  some  places  nearer  the  surface  than  others  but  probably 
vanishing  at  comparatively  shallow  depths.  The  relative  amounts  of 
steam  and  ground  water  at  any  particular  point,  the  rate  at  which 
the  water  percolates  and  the  rate  at  which  the  steam  rises  will  con¬ 
dition  the  temperature  of  the  resulting  hot  water  and  the  amount  of 
gases  retained  by  it.  The  rate  of  oxidation  also  will  have  a  controlling- 
influence,  for  the  more  sulphur  is  oxidized  the  less  hydrogen  sulphide 
will  escape  and  the  more  ammonia  will  be  held.  The  higher  solubility 
of  ammonia  in  water,  especially  where  acid  is  present,  no  doubt 


accounts  for  the  tendency  in  the  ratio 


H2S 

NH:i 


to  decrease  with  time,  as 


1  This  spring  occurs  on  the  other  side  of  a  high,  narrow  ridge  about  half  a  mile  to  the  west  of 
The  Geysers,  where  local  conditions  underground  may  be  somewhat  different. 

2  A  more  recent  survey  of  a  large  number  of  springs  in  the  Norris  Basin,  Yellowstone  Park, 
shows  that  there  also  with  few  exceptions  the  concentration  of  the  SO4  radical  is  much  lower  in 
the  alkaline  than  it  is  in  the  acid  springs. 


78 


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the  results  show  it  does  (see  table  14).  Portions  of  all  the  gases  will 
escape  to  the  drier  ground  nearer  the  surface  where  the  capillaries 
bring  them  into  contact  with  atmospheric  oxygen.  Here  oxidation 
should  be  most  rapid,  here  more  ammonia  should  be  fixed,  and  where 
undecomposed  rock  still  remains  magnesium  and  other  sulphates  will 
be  added  to  the  mixture.  The  solution  becomes  more  concentrated 
and  portions  of  it,  rising  to  the  surface,  crystallize  in  summer,  but 
when  the  autumn  rains  come  again  the  salts  are  dissolved  and  carried 
down  into  the  underground  circulation  and  eventually  reach  the 
springs. 

In  therapeutic  character  and  impliedly  in  composition  the  various 
springs  are  supposed  to  exemplify  great  diversity — a  belief  reflected 
in  their  names.  Variations  in  concentration  there  are,  of  course,  and 
to  some  extent  in  the  proportions  of  the  elements,  but  the  only  sig¬ 
nificant  distinction  to  be  drawn  is  the  one  which  divides  the  acid  from 
the  alkaline  springs.  It  is  true,  however,  in  this  particular  locality, 
that  differences  in  chemical  character  are  intimately  related  to  con¬ 
centration,  so  that  it  will  be  well  to  follow  the  latter  relation  a  little 
farther. 

If  the  hypothesis  just  presented  is  a  true  one,  springs  which  draw 
their  supply  from  ground  where  no  gases  rise  would  be  cold,  or 
when  a  limited  amount  of  gas  and  steam  rises  the  springs  would  be 
warm  and  of  low  concentration.  The  presence  or  absence  of  abnormal 
temperatures  and  the  differences  in  the  growth  of  vegetation  here  and 
there  in  The  Geysers  area  are  matters  dependent  on  the  degree  of 
permeability  of  the  ground  to  volcanic  gases,  including  steam.  In 
spots  where  formerly  there  was  little  or  no  fumarole  activity,  boring 
has  developed  an  ample  flow  of  steam  and  other  gases.  The  difference 
between  such  areas  and  the  more  active  ones  is  due  either  to  the 
absence  of  superficial  cracks  in  the  rock  or  to  more  or  less  obstruction 
of  the  cracks  by  rock  detritus.  The  high  concentrations  of  salts  which 
are  found  in  the  acid  springs  are  doubtless  derived  from  ground  readily 
permeable  to  volcanic  gases  and  to  air,  and  it  is  significant  that  all  the 
acid  springs  except  the  two  of  lowest  concentration  are  immediately 
contiguous  to  such  ground.  The  process  of  concentration  by  evapora¬ 
tion  may  continue  underground  to  some  extent  but  it  must  be  much 
less  important  there.  In  unusually  hot  weather,  evaporation  in  the 
spring  basins  seems  to  reach  a  high  figure,  for  at  such  times  the  water 
level  drops  suddenly  in  a  very  striking  way,  only  to  return  again 
during  the  night  or  in  a  cooler  interval  following,  although  no  rain 
falls,  but  this  must  obviously  affect  very  nearly  alike  all  springs 
exposed  to  the  sun,  whether  acid  or  alkaline,  and  can  have  no  bearing 
on  the  difference  between  them. 

We  have  noticed  that  the  alkaline  springs  are  usually  very  low  in 
mineral  matter  as  compared  with  the  acid  springs — a  fact  which  would 


80 


indicate  either  dilution  with  surface  water  in  the  former  or  a  source 
in  ground  where  oxidation  was  limited  (table  3).  As  a  matter  of  fact 
four  of  the  seven  alkaline  springs  analyzed1  occur  in  the  edge  of 
stream  beds  where  they  are  obviously  diluted  by  surface  water  when 
the  stream  is  high,  and  perhaps  in  lesser  degree  at  other  times.  Five 
of  the  springs  have  their  temperatures  maintained  by  steam  jets 
rising  in  their  very  basins,  and  the  presence  of  black  sulphide  in  them 
is  probably  a  direct  consequence  of  precipitation  by  the  hydrogen 
sulphide  on  the  spot.  A  spring  which  is  not  too  highly  diluted  by 
surface  water  may  in  this  way  be  maintained  at  the  boiling  point. 
The  other  two  alkaline  springs,  the  Magnesia  and  the  Bath-house 
springs,  are  of  relatively  low  temperature  (50°  to  60°  C.)  and  their 
occurrence  at  the  foot  of  slopes,  more  or  less  covered  with  grass,  weeds 
and  bushes  where  there  is  but  little  indication  of  fumarole  activity 
and  where  there  can  be  little  oxidation,  seems  to  be  connected  in  a 
perfectly  logical  way  with  the  low  concentration  of  the  fumarole 
products  we  find  in  them. 

The  relation  between  concentration  and  the  chemical  character  of 
the  waters  has  been  discussed  before  in  a  treatise  on  the  hot  springs 
of  the  Lassen  National  Park,2  but  it  is  of  course  highly  desirable  that 
observations  of  phenomena  which  are  the  result  of  complicated  con¬ 
ditions,  especially  where  the  conditions  are  not  subject  to  control, 
should  not  be  confined  to  a  single  locality.  At  The  Geysers  it  has 
been  possible  to  pursue  the  subject  somewhat  farther,  but  the  inves¬ 
tigation  has  led  to  identical  conclusions,  namely,  that  the  alkaline 
springs  here  result  from  the  chemical  action  of  waters  which  are  acid 
nearer  their  source;  that  the  acid  water  percolating  through  the 
ground  gradually  decomposes  the  rocks  it  encounters,  and  if  the 
process  continues  long  enough  the  acid  will  be  converted  into  neutral 
sulphates,  and  that  subsequent  to  this  the  chemical  character  of  the 
process  changes;  the  action  of  carbonic  acid  and  hydrogen  sulphide 
also,  if  any  of  the  latter  remains  (or  if  any  is  later  absorbed  by  the 
water  without  oxidation),  now  becomes  dominant,  with  the  result 
that  bicarbonates  and  carbonates,  sulphides  and  probably  hydro¬ 
sulphides  are  carried  into  solution,  giving  to  the  water  an  alkaline 
character.  This  much  can  be  safely  stated  from  a  knowledge  of  the 
chemical  reactions  between  certain  minerals  and  glasses  on  the  one 
hand,  and  hot  water  containing  the  two  mentioned  gases  on  the  other. 
But  further  knowledge  of  the  process  in  its  later  stages  is  needed — 
what  becomes  of  the  iron,  and  especially  the  alumina  in  the  rock, 
whether  they  form  sericite,  kaolin,  or  other  minerals,  and  where  they 
are  deposited,  are  questions  which  remain  undetermined. 

1  A  few  other  alkaline  springs  were  discovered,  most  of  them  seepages  issuing  near  the  Bath¬ 
house  spring  whose  waters  in  all  probability  are  of  the  same  character. 

2  Day  and  Allen,  op.  cit. ,  p.  164. 


81 


There  are  other  rational  ways  in  which  alkaline  spring  waters  may 
originate.  If  the  volcanic  gases  contain  no  sulphur  or  if  the  sulphur 
undergoes  no  oxidation,  the  waters  will  be  alkaline  from  the  first. 
Neither  of  these  conditions,  however,  is  fulfilled  at  The  Geysers;  the 
gases  always  contain  sulphur,  and  the  presence  of  sulphate  in  all  the 
alkaline  waters  shows  that  oxidation  must  have  occurred  somewhere 
in  the  course  of  their  underground  movement. 

That  the  sulphate  may  arise  from  the  oxidation  of  sulphide  or 
thiosulphate  is  a  view  not  entirely  shut  out.  There  appears  to  be 
no  convincing  evidence  that  either  of  these  reactions  has  ever  been 
observed  in  alkaline  solutions  through  the  agency  of  air  alone.  Oxi¬ 
dation  of  thiosulphates  to  sulphates  by  fungi1  under  certain  con¬ 
ditions  and  also  by  bacteria2  are  on  record,  but  whether  such  reactions 
may  occur  under  conditions  prevailing  in  hot  springs  is  another 
question.  The  concession  that  it  does  occur,  however,  has  no  im¬ 
portant  bearing  on  the  question  whether  these  alkaline  springs  are 
or  are  not  of  deep-seated  origin;  they  have  not  the  concentration  that 
should  belong  to  waters  formed  at  any  considerable  depth,  and  the 
field  evidence  is  all  against  that  view.  Neither  is  there  any  reason  to 
believe  that  the  acid  waters  were  ever  alkaline. 

Low  concentration,  therefore,  so  far  as  it  applies  to  the  sulphate  in 
alkaline  springs,  is  satisfactorily  accounted  for  in  the  foregoing,  either 
by  direct  dilution  of  a  water  originally  more  highly  mineralized  or 
by  the  contribution  of  little  mineral  matter  to  the  water  in  the  first 
place.  The  low  concentration  of  other  constituents  also,  like  silica, 
carbonate  and  bicarbonate,  agrees  well  with  the  slower  rate  of  action 
which  would  be  predicted  for  a  weak  acid  like  carbonic  acid  as  com¬ 
pared  to  the  action  of  sulphuric  acid  on  rocks. 

While  the  alkaline  springs  of  Iceland  and  the  Yellowstone  Park 
have  been  regarded  by  some  able  investigators  as  a  subsequent  phase 
in  the  development  of  springs  which  were  formerly  acid,  the  alkaline 
springs  at  The  Geysers,  like  those  in  the  Lassen  National  Park,  are 
to  be  regarded  as  contemporaneous  with  the  acid  springs  which  occur 
in  the  same  area.  The  facts  indicate  a  change  during  the  progress  of 
the  waters  underground  rather  than  a  distinct  period  of  development ; 
in  the  vents  where  the  waters  emerge  from  the  ground  there  is  no 
reason  to  suppose  that  they  were  ever  of  a  different  character. 

TEMPERATURE  GRADIENT 

No  question  is  more  vitally  related  to  the  genesis  of  hot  springs 
than  the  rate  at  which  the  temperature  of  the  ground  rises  from  the 
surface  downward.  It  is  certainly  much  greater,  at  least  in  some 
localities,  than  geologists  are  aware  of.  In  this  respect  drilling  opera- 

1  T.  Matsumoto,  Ann.  Missouri  Bot.  Garden  8,  1-62,  1921. 

2  W.  T.  Lockett,  Proc.  Roy.  Soc.  London  (B)  87,  441,  1914. 


82 


tions  at  The  Geysers  have  been  of  great  scientific  importance.  In 
1924  work  on  Well  3,  located  near  the  extreme  eastern  border  of  the 
area,  was  in  progress.  A  short  10-inch  iron  casing  extended  down  but 
a  few  feet  below  the  surface,  leaving  the  remainder  uncased.  The 
well  was  open  and  discharging  gases  and  steam.  Twice  we  were  able 
to  measure  temperatures  here.  They  were  taken  with  an  armored 
maximum  thermometer,  reading  in  single  degrees  from  50°  to  150°  C. 
Temperature  at  the  top  (the  bulb  9  inches  below  the  top  of  the 
casing)  was  111°  C.  increasing  gradually  to  126°  at  the  bottom,  which 
was  then  about  100  feet  down.  Boring  operations  were  continued  in 
the  well  until  a  depth  of  154  feet  had  been  reached,  when  a  drop  in 
temperature  occurred  which  was  attributed  to  an  underground  stream 
of  water.  In  any  event  the  temperature  gradient  was  disturbed  to 
such  an  extent  that  later  measurements  were  inconsistent  with  the 
former  ones.  This  well  was  drilled  by  the  old  churn-drill  system.  In 
May  1925  the  well  was  still  emitting  steam  and  a  thin  spray  of  water 
which  occasionally  reached  a  height  of  10  feet  (fig.  30).  The  tem¬ 
peratures  in  Well  3,  measured  on  May  26,  1925,  were  as  follows: 


Well  3.  Well  6. 


Depth 

Temperature 

Date 

Depth 

Temperature 

9  in. 

99°C. 

Mar.  24 

30  ft. 

164°C. 

10  ft. 

99 

250 

173.5 

33 

99 

25 

50 

159 

82 

100 

234 

168 

98 

101 

320 

170 

105 

102 

360 

170 

115 

104 

422 

170 

131 

110.2 

482  bottom 

170 

154 

112.5 

Well  8. 


Date 

Depth 

Temperature 

Mar.  25 

top 

610  ft. 

150°C. 

162 

Depths  were  measured  from  the  top  of  the  casing  which  projected 
about  3  feet  above  ground. 

That  the  temperature  gradient  in  Well  3  is  not  exceptional,  may 
be  seen  from  the  measurements  of  Wells  6  and  8,  made  at  our  request 
in  March  1926  by  J.  D.  Grant  and  Delano  Grant. 

Another  series  of  temperature  measurements  in  open  wells  was 
made  in  June  1926  by  one  of  the  authors  (Day).  Nearly  all  the  wells 


were  then  open  as  they  had  been  left  for  several  months  for  the  pur¬ 
pose  of  determining  in  a  rigorous  fashion  whether  any  diminution  in 
steam  supply  would  result.  With  the  aid  of  the  driller,  Mr.  Cooper, 
and  his  assistant,  a  temporary  fall  was  rigged  at  Wells  2,  4  and  5. 


Fig.  30 — Well  No.  3  as  it  appeared  in  1925.  Casing  is 
coated  with  opal  formed  by  evaporation  of  small 
amount  of  water  constantly  thrown  out  with  steam. 


At  No.  8  the  regular  drill  rigging  was  used.  To  the  fall  was  attached 
a  steel  drill  rod  sharpened  at  the  lower  end,  to  which  the  armored 
thermometer  was  securely  fastened  so  that  it  could  be  raised  or 
lowered  in  the  well.  Measurements  in  Wells  2,  4  and  8  were  entirely 
successful,  but  the  rod  was  blown  out  of  Well  5  by  the  steam  and  the 
thermometer  broken.  The  measurements  recorded  below  were  made 


84 


at  the  top  of  the  wells  mentioned,  at  the  bottom  of  the  casing  and  at 
the  bottom  of  the  well. 


Well  temperatures  with  steam  flowing  freely. 


Well  2: 

Bottom  of  well . 

Bottom  of  casing . 

Top  of  well . 

Well  4: 

Bottom  of  well . 

Bottom  of  easing . 

Top  of  well . 

Well  8: 

Bottom  of  well . 

Bottom  of  well  (2d  meas.) 

Bottom  of  easing . 

Top  of  well . 


Depth 


320  ft. 
130 


451 

25G 


63  G 
636 
160 


Temperature 


168. 6°C. 

167.5 

165 . 6 

172.6 
169 
163.4 

157.2 

156.6 
153.9 
150 


We  have,  therefore,  three  independent  series  of  temperature  meas¬ 
urements  in  open  steam  wells  made  by  three  different  observers,  all 
of  which  show  a  temperature  gradient. 

An  effort  was  also  made  to  measure  the  gradient  in  two  of  the 
closed  wells.  For  actual  tests  we  are  indebted  to  Mr.  Galloway,  the 
engineer,  and  his  aides,  especially  to  Mr.  Butler,  who  was  in  imme¬ 
diate  charge  of  operations  on  the  ground  at  the  time.  The  tests  were 
made  on  Well  5  with  test-metals  melting  respectively  at  600°  F. 
(315°  C.),  500°  F.  (270°  C.)  and  450°  F.  (232°  C.).  The  test-metals 
in  small  chips  were  inclosed  in  very  short  lengths  of  %-inch  pipe 
capped  at  both  ends.  To  make  it  possible  to  lower  these  metals  into 
the  well,  the  vertical  steel  outlet  pipe  (8  inches  in  diameter)  was 
threaded  at  the  top  to  fit  a  heavy  conical  cap,  through  the  apex  of 
which  a  small  hole  (1/16  to  1/8  inch)  was  drilled.  A  reel  of  steel 
wire  500  feet  in  length  and  about  1  mm.  in  diameter  was  unwound 
for  a  few  yards  and  the  free  end  pushed  through  the  top  of  the  cap 
after  which  the  test-metals  and  their  receptacles  were  attached.  The 
cap  was  then  screwed  down  and  the  valve  of  the  well  opened.  The 
steam  which  escaped  from  the  small  bore-hole  in  the  cap  was  hardly 
visible  and  offered  no  obstruction  to  the  lowering  of  the  metals.  They 
were  therefore  dropped  to  a  depth  of  250  feet  and  held  15  minutes. 
When  they  were  drawn  up  and  the  receptacles  had  been  removed  and 
opened,  only  one  metal,  that  melting  at  232°,  was  completely  melted 
down — the  other  chips  were  intact.  A  test  in  the  side  pipe  at  the 
same  time  with  the  maximum  thermometer  showred  a  temperature  of 
185.5°  C.  at  the  top  of  the  well  (closed).  Inside  of  250  feet  the  tem¬ 
peratures  therefore  rose  at  least  46°  C.,  but  less  than  85°  C.  In  a 
second  test  the  metals  w^ere  lowered  to  the  bottom,  where  they  were 


85 


kept  15  minutes.  When  removed  it  was  found  that  neither  of  the 
other  two  metals  had  been  affected.  The  temperature  between  250 
feet  and  416  feet  could  not  therefore  have  risen  as  much  as  38°,  and 
possibly  not  at  all.  Another  trial  at  Well  4,  in  which  a  maximum 
thermometer  was  lowered  in  a  similar  way,  was  unfortunate;  the  pipe 
which  inclosed  it  got  caught — probably  under  a  projecting  rock  in 
the  wall  of  the  well — and  was  lost.  The  operation  as  described 
appears  easy,  but  the  actual  risk  of  getting  burned  which  the  work¬ 
men  incurred  was  so  great  that  we  did  not  care  to  urge  another 
attempt. ' 

The  tests  at  Well  5  show  that  no  very  high  temperature  is  to  be 
found  at  the  bottom  as  the  workmen  had  been  inclined  to  believe; 
the  drawing  of  the  temper  in  the  drill,  which  they  observed,  must 
have  been  due  to  local  heating  by  friction.1 

Wherever  temperatures  have  been  measured  in  deep  holes  of  the 
earth's  crust  a  gradient2  has  been  found,  whether  the  hole  is  filled 
with  air  or  water.  Even  wells  filled  with  rapidly  escaping  steam,  as 
now  appears,  are  no  exception8  to  the  rule.  If  a  gradient  is  found 
where  the  steam  is  escaping  it  should  not  be  surprising  to  find  it  more 
strongly  marked  when  the  well  is  closed.  The  condition  of  saturation 
which  was  discovered  in  the  steam  after  the  wells  had  been  closed  for 
some  time  is  evidently  confined  to  the  top  of  the  well  where  prac¬ 
tically  all  the  heat  loss  takes  place  and  where,  if  anywhere,  con¬ 
densation  of  steam  would  be  looked  for.  The  water  perhaps  accumu¬ 
lates  in  the  horizontal  pipe  attached  to  the  casing;  it  can  hardly  drip 
down  to  any  considerable  depth  without  vaporizing,  or  the  gage 
would  show  a  higher  pressure  than  it  does,  whereas  if  steam  without 
water  exists  in  the  depths  of  the  well  superheating  would  be  necessary 
in  order  to  balance  the  pressure  of  the  saturated  steam  at  the  top. 

In  its  geological  bearing,  one  of  the  most  important  facts  that 
drilling  operations  at  The  Geysers  has  disclosed  is  that  within  a  depth 
of  500  feet  from  the  surface  a  rise  of  130°  to  165°  C.  is  encountered.4 
This  rise  in  temperature,  to  be  sure,  is  not  comparable  to  an  ordinary 
earth  gradient;  it  is  due  no  doubt  to  ascending  currents  of  steam  and 
varies  with  the  rate  of  the  steam  flow — an  agency  particularly  effec¬ 
tive  in  heating  water.  Whatever  its  ultimate  source,  we  have  here — 
even  under  natural  conditions — a  supply  of  heat  abundantly  adequate 
both  in  temperature  and  amount  to  account  for  all  the  hot  springs  in 
the  vicinity,  and  there  is  obviously  not  the  least  necessity  to  assume 

1  See  N.  L.  Bowen  and  M.  Aurousseau,  Fusion  of  sedimentary  rocks  in  drill  holes,  Bull.  Geol. 
Soc.  Amer.,  34,  431,  1923. 

2  C\  E.  Van  Orstrand,  personal  communication. 

3  The  uniformity  in  temperature  from  top  to  bottom  in  the  shallow  wells  of  Hawaii  may  now 
be  ascribed  to  the  saturated  condition  of  the  steam. 

4  Reckoning  from  the  variable  surface  temperature  in  the  hot  area  itself. 


86 


that  the  springs  consist  of  surface  water  which  has  been  heated  by 
descending  to  great  depths,  even  if  we  accept  the  theory  as  otherwise 
satisfactory — a  concession  which  is  not  warranted  in  the  case  before  us. 

CAUSE  OF  THE  HEAT 

Many  causes  for  the  heat  of  hot  springs  have  been  advanced  by 
geologists.  Waring,  who  has  had  wide  opportunities  for  observation, 
mentions,  in  his  well-known  Springs  of  California,  to  the  text  of 
which  the  reader  is  referred,  eleven  cases  where  the  water  may  derive 
its  heat  from  hot  rocks  by  descending  to  great  depths;  two  cases  where 
chemical  action  may  be  the  cause  of  the  heat,  and  seven  instances 
where  the  heat  may  have  originated  in  earth  movements  responsible 
for  the  alteration  of  sediments  in  which  the  springs  occur.  In  more 
than  fifty  groups  of  hot  springs,  Waring  mentions  the  proximity  of 
lavas  or  intrusives,  implying  the  possibility  that  they  may  still  retain 
residual  heat,  while  in  a  similar  number  of  places  he  draws  attention 
to  the  association  of  hot  springs  with  faults.  The  last  point  is 
regarded  by  the  writer  as  especially  important,  as  a  summary  para¬ 
graph  on  temperature  (op.  cit.  p.  24)  makes  clear.  Waring  there  says: 

“  Observations  of  the  temperature  in  deep  mines  and  deep  borings  indicate  that  in 
regions  of  comparatively  uniform  and  undisturbed  rock  below  the  first  50  feet  (in  which 
the  underground  temperature  is  affected  by  seasonal  variation  in  temperature  of  the 
air)  the  temperature  increases  at  the  rate  of  1°F.  for  about  each  50  or  60  feet  of  increase 
in  depth.  In  favorable  localities  this  increment  may  be  safely  assumed  in  estimating 
the  depth  from  which  the  heated  water  rises.  In  the  greater  number  of  places  where 
thermal  springs  issue,  however,  this  increment  is  valueless  as  a  basis  for  estimating 
the  depth  from  which  the  water  rises.  The  high  temperatures  of  the  water  of  most 
hot  springs  can  usually  be  assigned  to  faults  or  displacements  in  the  rock  formations, 
to  volcanic  activity,  or  to  chemical  action  rather  than  to  normal  increase  of  tempera¬ 
ture  with  depth.  The  rocks  along  fault  lines  are  probably  heated  considerably  above  a 
normal  temperature  by  the  great  pressure  and  friction  that  have  been  produced. 
Water  from  deep  sources  moves  upward  along  these  zones  and  is  additionally  heated 
by  contact  with  the  heated  rocks.  In  some  areas  of  volcanic  rocks  there  are  probably 
masses  below  the  surface  that  have  not  yet  cooled  to  a  normal  temperature,  and  they 
heat  water  which  comes  near  them.  Chemical  reactions — notably  the  oxidation  of 
pyrite — liberate  heat  and  may  increase  the  temperature  of  underground  water.” 

Other  geologists  have  regarded  radioactivity  as  a  probable  source 
of  the  heat,  and  finally  economic  geologists,  or  some  of  them,  have 
inclined  to  the  view  that  the  water  of  hot  springs  may  be  very  largely 
magmatic,  bringing  up  its  heat  from  the  magma  itself.  The  deriva¬ 
tion  of  the  heat  supply  of  hot  springs  from  radioactivity  has  been 
touched  upon  by  the  authors  in  a  former  treatment  of  this  subject.1 
It  was  pointed  out  in  that  place  that  a  high  degree  of  radioactivity  in 
mineral  deposits  bore  no  relation  to  local  high  temperatures,  and  two 
investigations  of  importance  bearing  directly  on  the  point  at  issue 

1  Day  and  Allen,  op.  cit.,  p.  150. 


87 


were  instanced;  an  investigation  by  Schlundt  and  Moore  in  the  Yel¬ 
lowstone  Park  and  an  investigation  by  Thorkelsson  in  Iceland,  in  both 
of  which  it  had  been  concluded  that  radioactivity  had  no  connection 
with  the  abnormal  temperatures  in  those  well-known  hot-spring 
localities. 

The  notion  that  the  high  temperatures  of  springs  and  fumaroles  is 
a  consequence  of  the  oxidation  of  pyrite  may  have  arisen  from  the 
observation  of  the  spontaneous  combustion  of  coal  in  mines  where 
the  veins  frequently  carry  considerable  pyrite.  However  it  may  be 
in  other  places,  at  The  Geysers  there  is  positive  evidence  against  the 
assumption;  drilling  has  shown  that  the  rock  underlying  the  decom¬ 
posed  material  at  the  surface  contains  only  a  small  amount  of  pyrite 
— and  that  quite  unoxidized.  Samples  of  the  rock  from  Well  2  taken 
from  depths  between  150  and  200  feet  were  examined  by  Wright  and 
by  Merwin.  All  were  sandstone  carrying  a  very  little  pyrite.  An 
analysis  of  a  sample  from  a  depth  of  150  feet  is  appended: 

Sandstone  from  Well  2. 


Si02 .  67.46 

Ti02 .  .44 

A1203 .  15.34 

Fe203 .  1.16 

FeO .  2.35 

CaO .  1.02 

MgO .  1.42 

Na20 .  3.03 

KoO .  2.65 

H20  (total) .  3.26 

P205 . 11 

FeSa .  1.93 


100.17 

The  pyrite  in  this  sample  amounted  to  1.93  per  cent  and  it  was 
very  bright.  A  microscopic  analysis  by  Merwin  disclosed  in  addition 
to  pyrite  only  quartz  and  sericite.  A  sample  of  the  rock  blown  out 
of  Well  6  consisted  of  shaly  sandstone  also  carrying  a  little  pyrite 
(bright)  and  a  veinlet  of  calcite.  A  sample  from  Well  4  was  of 
similar  character.  A  core  taken  from  Well  5  at  a  depth  of  230  feet 
was  examined  in  thin  section  and  found  to  be  gabbro  also  containing 
a  little  pyrite.  In  a  sample  of  chert  from  Well  8,  pyrite  was  found 
in  somewhat  greater  amount  than  usual  and  it  was  also  dense  and 
bright.  These  latter  examinations  were  all  made  by  Wright.  In 
Well  3,  J.  D.  Grant  reported  that  no  pyrite  was  found.  While  this 
work  is  not  a  systematic  survey  of  the  different  wells  from  top  to 
bottom,  no  observations  have  shown  any  considerable  amount  of 
pvrite  anywhere  and  if  a  mass  of  it  had  been  struck  in  any  place  it  is 
inconceivable  that  a  mineral  of  such  distinctive  properties  should  not 
have  revealed  itself  either  by  its  hardness  or  by  its  color,  luster  and 
density  in  the  drillings  as  they  were  washed  out. 


88 


In  the  Lassen  Park  where  evidence  from  drilling  was  not  available, 
the  possibility  of  heat  from  chemical  action  was  considered  at  some 
length  and  the  conclusion  was  reached  that  neither  the  oxidation  of 
pynte  nor  the  decomposition  of  lavas  could  be  rapid  enough  to  raise 
the  temperature  in  any  considerable  degree.1 

Waring,  as  we  have  seen,  decides  against  the  view  that  hot-spring 
waters  generally  derive  their  heat  from  hot  rock  by  descending  to 
great  depth,  though  this  theory  is  probably  commonly  held.2  That 
the  average  earth  gradient  has  no  application  in  most  hot-spring 
areas,  as  Waring  believes,  is  confirmed  so  far  as  The  Geysers  is  con¬ 
cerned  by  the  facts  discovered  in  drilling. 

Against  the  general  acceptance  of  the  theory  that  the  water  of  hot 
springs  has  been  heated  by  descending  to  great  depths  is  also  the 
escape  of  volcanic  gases  in  all  the  hot-spring  districts  yet  observed  by 
the  authors,  including  some  twenty-five  groups  altogether,  and  further 
study  of  the  literature  permits  the  conclusion  that  the  presence  of 
volcanic  gases  is  the  rule  if  not  universal.  When  considered  in  its 
general  aspects  this  occurrence  of  volcanic  gases  is  of  profound  sig¬ 
nificance;  it  is  the  one  thread  logically  connecting  all  phases  of  igneous 
activity,  the  cause  alike  of  the  volcanic  explosions  with  their  imposing 
steam  clouds,  the  rise  of  lava  in  craters,  the  intense  surface  tempera¬ 
tures  in  some  volcanic  eruptions,  the  formation  of  fumaroles  with 
their  various  characteristics,  and  finally  of  the  heat  of  hot-spring 
waters  and  of  the  distinctive  features  in  hot-spring  areas.  According 
to  this  theory  the  function  of  faults  is  to  permit  the  escape  of  vol¬ 
canic  gases  with  their  associated  heat  from  the  magma  or  batholith. 
What,  otherwise,  should  be  the  significance  of  the  association  of  vol¬ 
canoes,  as  well  as  fumaroles  and  hot  springs,  with  faults? 

It  is  a  known  fact  that  all  igneous  rocks,  even  when  quite  unaltered, 
give  off  large  volumes  of  gases,  the  chief  of  which  is  steam,  when  they 
are  heated  to  high  temperatures,3  and  it  was  Gautier4  who  first 
pointed  out  that  these  gases  were  of  similar  composition  to  the  vol¬ 
canic  gases.  Indeed  it  is  a  chemical  necessity  that  the  gases  should 
escape  if  the  rock  is  sufficiently  hot,  and  a  mode  of  escape  is  offered, 
as  it  should  be,  by  the  association  with  faults  of  sufficient  depth. 

The  consequences  of  this  view  have  been  discussed  in  the  earlier 
paper  so  often  referred  to,  where  it  was  shown  that  the  condensation 
of  steam  by  ground  water  furnished  the  most  probable  means  for  the 
transmission  of  heat  from  the  depths;  that  the  variable  temperatures 
of  many  springs  at  different  times  of  the  year,  the  spouting  of  springs, 

1  Day  and  Allen,  op.  cit.,  pp.  151-153. 

2  See  C.  E.  Van  Orstrand,  Jour.  Geol.,  32,  194,  1924. 

3  R.  T.  Chamberlin,  Gases  in  Rocks,  Carnegie  Inst.,  Wash.  Pub.  No.  106,  1908;  Arthur  L.  Day 
and  E.  S.  Shepherd,  Water  and  Volcanic  Activity,  Bull.  Geol.  Soc.  Am.  24,  573-606,  1913; 
E.  S.  Shepherd,  The  Analysis  of  Gases  obtained  from  Volcanoes  and  from  Rocks,  J.  Geol.,  33, 
289,  1925. 

4  Compt.  rend.,  132,  61,  189,  and  932,  1901;  136,  16,  1903. 

Ti  t* 


89 


their  transformation  into  fumaroles  and  vice  versa,  and  finally  the 
disappearance  of  springs  and  new  outbreaks  of  thermal  activity  are 
all  readily  accounted  for  on  the  basis  of  this  fundamental  assumption. 


ORIGIN  OF  STEAM  AT  THE  GEYSERS 


The  hypothesis  that  hot  springs  are  fed  by  ground  water  heated 
and  augmented  by  magmatic  steam  which  is  condensed  in  the  heating 
process  was  deduced  in  large  measure  from  general  considerations— 
the  composition  of  rocks  and  their  behavior  on  heating;  rock  decom¬ 
position  with  chemical  reagents;  and  general  physical  relations  of 
hot  springs  and  fumaroles.  A  detailed  field  application  of  the  idea 
had  been  possible  only  in  the  Lassen  National  Park  where  superheated 
steam  had  been  actually  found  in  only  one  place.  When,  therefore, 
the  hot  springs  at  The  Geysers  were  found  to  be  associated  with  a 
supply  of  hot  steam  generally  distributed  not  far  below  ground,  the 
discovery  was  naturally  hailed  as  a  confirmation  of  previous  views. 
But  of  course  it  is  realized  that  the  magmatic  origin  of  this  steam  can 
not  command  the  assent  of  geologists  until  the  new  knowledge  that 
has  come  to  light  in  the  development  of  the  wells,  and  the  tests  made 
on  them,  has  been  carefully  considered  from  this  viewpoint. 

Any  satisfactory  theory  of  its  origin  must  take  full  account  of  the 
huge  volume  of  the  steam,  its  high  temperature  and  pressure,  and  its 
superheated  condition.  When  the  mild  character  of  the  original  sur¬ 
face  activity  at  The  Geysers  is  compared  with  the  immense  steam- 
flow  of  today  the  contrast  is  truly  amazing — doubly  so  it  must  be  to 
one  who  holds  that  the  steam  is  derived  entirely  from  ground  water. 
Whatever  previous  views  one  may  have  had  concerning  hydrothermal 
activity,  the  facts  brought  to  light  in  this  field  should  convince  him 
that  the  immediate  origin  of  the  steam  lies  at  a  very  considerable 
depth.  The  steam- wells  of  California  have  been  carried  down  to 
depths  of  nearly  650  feet,  those  of  Tuscany  to  about  the  same  depth, 
and  while  it  can  not  be  said  that  temperature  is  proportional  to  depth, 
the  deeper  a  well  is  drilled  in  either  locality  the  greater  the  steam-flow 
and  the  hotter  the  steam. 

As  to  the  situation  in  California,  the  more  one  ponders  the  question 
the  more  difficult  it  is  to  conceive  that  a  body  of  ground  water  of  any 
great  magnitude  can  penetrate  even  to  such  depths  as  a  few  hundred 
feet.  Where  cracks  or  seams  exist,  water  will  doubtless  penetrate  if 
the  steam  pressure  it  encounters  is  not  prohibitive,  but  the  water 
must  be  much  more  copious  than  it  is  here  to  penetrate  far  in  such 
seams  without  being  again  vaporized.  It  is  conceded  that  the  ground 
temperature  at  any  point  and  level  is  not  so  great  before  drilling  as 
afterwards,  but  it  must  be  well  above  boiling  at  depths  say  of  100 
feet,  except  in  places  where  no  perceptible  amount  of  steam  is  rising; 
where  steam  can  not  find  its  way  up,  surely  water  can  not  find  its 


90 


way  down!  It  is  conceivable  that  ground  water  under  sufficient  head 
might  penetrate  to  a  considerable  depth  about  the  periphery  of  a 
body  of  hot  rock  and  that  a  vaporized  portion  of  it  might  be  fed  into 
the  cracks  of  the  rock,  under  pressure,  but  admitting  that  possibility 
the  facts  point  to  a  surface  configuration  in  no  way  adapted  to  such 
water  storage  and  a  body  of  ground  water  wholly  inadequate  to 
supply  continuously  such  volumes  of  steam. 

SUPERHEATED  CONDITION  OF  THE  STEAM 

The  matter  of  reconciling  the  superheated  condition  of  the  steam 
with  the  conception  that  it  is  continuously  supplied  by  a  store  of 
ground  water  is  fraught  with  some  difficulty,  which  had  perhaps  best 
be  left  to  the  proponents  of  the  theory.  On  the  other  hand,  if  the 
steam  is  derived  from  a  magma  it  would  necessarily  be  superheated  at 
its  source. 

For  readers  unfamiliar  with  geology  it  may  be  said  that  the  magma 
is  the  moulten  fluid  from  which,  in  cooling,  the  igneous  rocks  are 
formed,  and  that  it  is  supposed  to  differ  from  flowing  lava  only  in  its 
higher  percentage  of  volatile  matter.  Even  after  it  has  become  cold 
and  solid,  considerable  quantities  of  the  volcanic  gases,  the  chief  of 
which  is  steam,  may  still  be  driven  out  of  it  by  heating  again.  The 
pitchstones — lava  which  has  solidified  as  glass,  and  is  therefore  more 
like  the  original  magma  than  are  the  crystalline  igneous  rocks — con¬ 
tain  sometimes  as  much  as  10  per  cent  by  weight  of  water,1  and  we 
infer  that  the  magma  contained  more,  as  it  is  hardly  credible  that 
some  water  was  not  lost  while  the  magma  was  in  the  heated  condition. 
Rocks  which  are  formed  from  a  magma  by  slow  cooling,  as  they  must 
be  when  formed  at  considerable  depth  in  the  crust  of  the  earth,  are 
entirely  crystalline  and  these  crystalline  rocks  contain  little  water, 
0.5  per  cent  on  the  average;  so  that  large  bodies  of  magma  buried  at 
considerable  depth  in  the  earth’s  crust  may  be  expected  to  give  off 
large  volumes  of  steam  for  a  long  period  of  time.  The  capacity  of 
molten  silicates  to  absorb  steam,  its  release  during  the  crystallization 
of  the  silicates  and  the  pressures  which  may  develop  thereby  are 
questions  which  have  been  experimentally  studied  by  Morey,2  by 
whose  work  our  conceptions  of  the  magma  have  been  confirmed 
and  extended.  The  magma  is  thus  a  solution,  one  important  con¬ 
stituent  of  which  is  water,  and  the  pressure  of  the  steam  it  emits  must 
be  lowered  by  the  mineral  matter  associated  with  it,  as  always  happens 
when  steam  escapes  from  a  solution.  In  short  the  steam  must  be 
superheated.  But  though  superheated  at  the  source,  it  may  of  course 
become  saturated  by  a  sufficient  reduction  of  temperature  or  by  a 

1  Cf.  J.  W.  Judd  et  al,  Eruption  of  Krakatoa  and  Subsequent  Phenomena,  p.  36  (Rept  of 
Krakatoa  Com.  Roy.  Soc.  London,  1888). 

2  G.  W.  Morey,  J.  Wash.  Acad.  Sci.,  12,  219,  1922;  J.  Geol.,  32,  291-295,  1924. 


91 


sufficient  reduction  of  both  temperature  and  pressure  in  unequal 
degree.  That  a  large  reduction  in  temperature  has  occurred  by  the 
time  the  steam  reaches  the  surface,  assuming  its  magmatic  origin, 
seems  certain  from  what  we  know  of  the  temperature  at  which  steam 
is  driven  out  of  the  igneous  rocks  and  from  the  copious  steam-flow 
developed  by  drilling.  It  is  by  no  means  improbable  that  a  large 
reduction  in  pressure  has  also  occurred.  For  the  moment,  however, 
we  would  fix  attention  on  the  fact  that  if  the  source  of  steam  at  The 
Geysers  is  magmatic,  its  large  volume  and  its  unsaturated  condition 
are  readily  explained. 

TRANSMISSION  OF  STEAM  FROM  ITS  SOURCE  TO  THE  SURFACE 

The  principal  facts  about  the  steam  flow,  that  it  may  be  developed 
by  boring  anywhere  within  the  hot  area,  that  it  increases  with  depth 
but  not  regularly,  that  boring  gives  rise  to  steam  wells  which  when 
closed  stand  at  widely  different  pressures,  and  that  each  well  after  a 
period  of  discharge  returns  when  closed  again  to  its  former  pressure — 
all  have  been  stated  in  the  foregoing.  Determinations  of  maximum 
pressure  indicate  that  it  is  constant  or  nearly  so  in  the  same  well.  A 
long  record  for  the  oldest  wells  and  the  investigations  described  on 
pp.  59-63  support  this  statement.  The  facts  show  clearly  that 
the  rock  is  not  equally  pervious  to  steam  in  all  directions, 
indeed  they  indicate  that  it  is  not  permeable  in  any  direction 
to  an  appreciable  degree,  for  there  is  nothing  in  the  overlying 
sediments  except  stratification  which  could  transmit  steam  in 
one  direction  more  readily  than  another,  and  while  it  is  conceivable 
that  stratified  rocks  suitably  tilted  might  transmit  steam  vertically 
with  special  facility,  they  must  inevitably  transmit  it  more  readily 
in  one  horizontal  direction,  which  is  not  the  case  here.  The  ordinary 
view  that  the  steam  reaches  the  surface  through  cracks  explains  the 
facts  in  a  measure.  That  the  cracks  can  not  be  open  to  any  appre¬ 
ciable  width  at  least  throughout  their  whole  depth  must  be  obvious. 
The  fault  if  it  exists,  as  we  assume,  instead  of  being  an  unimpeded 
passage  to  the  depths  is  probably  a  zone  or  band  of  rock  shattered  by 
an  irregular  system  of  seams  long  enough  and  narrow  enough  to 
interpose  a  high  resistance  to  the  passage  of  gases.  Such  an  hypothe¬ 
sis  would  explain  the  difference  in  activity  wffiich  is  found  in  different 
fumarole  regions.  Thus  the  greater  steam  flow  and  much  higher 
temperatures  in  the  natural  fumaroles  of  Tuscany  than  in  those  at 
The  Geysers  should  be  due  to  the  slighter  impediment  which  the 
steam  in  the  former  locality  encounters  in  its  ascent  to  the  surface. 
It  may  possibly  be  affected  also  by  a  higher  steam  pressure  at  the 
source,  but  a  variation  in  this  factor  alone  could  not  explain  the  facts, 
since  drilling  at  The  Geysers  makes  apparently  a  far  greater  differ¬ 
ence  than  it  does  in  Tuscany.  The  irregularities  in  thermal  activity 


92 


in  different  parts  of  the  same  area  may  be  accounted  for  in  the  same 
way. 

On  the  other  hand  while  the  hypothesis  serves  well  in  explaining 
the  increase  of  steam  flow  with  depth  it  does  not  satisfactorily  explain 
the  increase  of  pressure,  for  the  figures  (pp.  56-57)  prove  that  wells 
which  emit  the  greatest  quantities  of  steam  do  not  necessarily  possess 
the  highest  pressure. 

The  increase  of  pressure  everywhere  with  depth  shows  clearly  that 
at  the  source,  whatever  and  wherever  that  may  be,  the  pressure  must 
be  much  higher  than  it  is  in  any  of  the  wells.  Within  the  realm  of 
laboratory  experience,  to  be  sure,  two  gas  reservoirs  connected  by 
even  the  finest  capillaries  can  not  remain  for  any  length  of  time  at 
very  different  pressures,  but  where  gases  are  forced  to  traverse  fine 
tortuous  seams  for  perhaps  thousands  of  feet  the  conditions  obviously 
transcend  any  with  which  we  are  familiar. 

DURATION  OF  THE  WELLS 

Very  interesting  scientifically  and  obviously  important  from  the 
industrial  viewpoint  is  the  question  how  long  these  wells  will  continue 
to  flow,  and  whether  they  will  maintain  their  pressure  unabated  for 
any  considerable  time.  The  data  on  this  point  are  confessedly  inade¬ 
quate  to  constitute  a  safe  basis  for  prophecy.  Ginori  Conti  says  of 
the  Tuscan  fumaroles  that  “as  far  as  it  has  been  possible  to  trace, 
they  appear  to  have  been  known  since  the  thirteenth  century."  The 
great  geyser  regions  are  doubtless  losing  a  prodigious  amount  of  heat. 
Iceland  is  the  only  one  of  these  which  has  been  long  known  to  the 
white  man.  Records  of  the  Iceland  geysers  are  said  to  extend  back 
about  seven  hundred  years,1  but  naturally  they  are  not  of  such  a 
character  as  to  prove  or  disprove  a  decline.  The  Yellowstone  Park 
has  been  the  most  studied.  Hague2  says  of  it  that  “new  springs  are 
constantly  breaking  out  and  old  ones  are  disappearing,”  but  in  his 
opinion  there  is  nothing  to  indicate  that  any  general  decline  has 
occurred  within  the  forty  years  during  which  the  Park  had  then  been 
under  observation.  Frank  J.  Haynes  and  his  son  J.  E.  Haynes  who 
have  observed  the  geysers  constantly  during  the  summer  season  from 
1881  to  the  present  time  confirm  this  view. 

On  the  other  hand  the  Katmai  fumaroles  have  undergone  a  very 
perceptible  decline  in  temperature  inside  of  five  years.  The  first 
temperature  measurements  were  made  there  in  1918  by  Savre  and 
Hagelbarger.3  Another  series  of  temperatures  taken  the  following 
year4  indicated  a  decline.  In  1923  Fenner’’  made  a  second  survey  of 

1  See  C.  S.  Forbes,  Iceland;  its  Volcanoes,  Geysers  and  Glaciers,  p.  241,  London,  1860. 

2  Bull.  Geol.  Soc.  Amer.,  22,  114,  1911. 

3  Ohio  Jour.  Sci.,  19,  249,  1919. 

4  Allen  and  Zies,  op.  cit.,  p.  108. 

6  J.  Geol.  33,  195  and  212,  1925;  also  personal  communication. 


the  region  and,  being  provided  with  a  map  locating  the  hottest 
fumaroles  found  by  his  predecessors,  tested  the  temperatures  of  the 
same  fumaroles  with  small  disks  of  lead,  tin  and  zinc.  All  these  hot 
fumaroles  had  declined  in  temperature,  while  the  general  aspect  of 
the  region,  which  Fenner  had  seen  in  1919,  as  well  as  the  appearance 
of  numerous  hot  springs  since  the  earlier  date,  constituted  unques¬ 
tionable  proof  of  a  general  fall  in  temperature.  The  Katmai  tem¬ 
peratures,  however,  were  measured  only  a  few  years  after  the  original 
eruption  of  igneous  matter  in  which  they  are  found,  and  being 
exceptionally  high  may  very  well  decline  at  a  diminishing  rate  as 
time  goes  on,  and  the  store  of  heat  there  may  still  be  very  large.  On 
the  other  hand  it  may  be  that  effective  steam  flow  there  will  be  of 
short  duration  because  the  source  of  heat  seems  to  be  unusually  near 
the  surface. 

In  any  attempt  to  forecast  the  future  of  the  steam  output  at  The 
Geysers  one  factor  obviously  must  not  be  lost  sight  of;  whatever  the 
supply  of  heat  and  steam  and  whatever  the  source  of  it,  the  output 
of  the  steam-wells  as  compared  to  the  natural  fumaroles  is  enormous 
and  it  is  not  therefore  to  be  expected  that  the  life  of  the  wells  could 
be  comparable  to  that  of  the  natural  fumaroles.  On. the  other  hand, 
the  great  industrial  drafts  upon  the  steam  supply  at  Larderello  which 
extend  back  apparently  to  1906  and  the  five  years  of  observation  at 
The  Geysers  both  attest  a  very  great  store  of  energy.  It  is  also  a 
fact  worthy  of  some  emphasis  that  the  extremely  dry  winter  and 
spring  of  1923-4,  which  was  responsible  for  the  cutting  down  of  the 
output  of  the  water-power  development  of  California  from  25  to  50 
per  cent  during  the  summer  of  1924,  exercised  no  measurable  influence 
upon  the  steam  flow  at  The  Geysers. 

THERMAL  ACTIVITY  AT  OTHER  POINTS  ALIGNED  WITH 

THE  GEYSERS 

Thermal  activity  similar  in  character  to  that  manifested  at  The 
Geysers  is  found  at  intervals  along  Sulphur  Creek  for  a  distance  of 
about  six  miles.  It  is  confined  entirely  to  a  narrow  belt  on  the  north 
side,  less  than  a  quarter  of  a  mile  in  width.  In  the  vicinity  of  The 
Geysers  there  are  a  few  slight  indications  of  former  activity  on  the 
south  side,  but  there  is  none  today1  and  none  elsewhere  on  that  side 
so  far  as  our  observations  extend. 

At  many  points  within  this  belt  ground  temperatures  a  few  feet 
below  the  surface  reach  nearly  to  the  boiling  point  of  water  for  the 
elevation,  but  in  most  of  these  places  the  amount  of  heat  escaping 
from  springs  and  steam  vents  is  obviously  slight  compared  to  that 
lost  by  the  undisturbed  ground  at  The  Geysers.  One  of  the  most 

1  With  the  exception  of  a  single  cold  vent  near  the  hotel  from  which  hydrogen  sulphide  is 
escaping. 


94 


active  of  these  areas  lies  just  over  the  high  ridge  to  the  west  of  The 
Geysers — a  comparatively  short  distance  from  Geyser  Creek.  There 
are  a  number  of  acres  of  barren  steaming  ground  where  boiling  tem¬ 
peratures  are  met  with  in  many  spots.  On  the  southern  border  the 
soft  treacherous  earth  is  dotted  with  sluggish  solfataras  lined  with 
sulphur  needles,  and  in  summer  time  it  is  more  or  less  incrusted  with 
salts.  The  Lemonade  Spring,  an  analysis  of  which  is  given  in  table  3, 
and  a  few  other  acid  springs  are  fed  in  part  by  the  drainage  from  this 
area.  A  quarter  of  a  mile  to  the  west  in  a  deep  narrow  gulley  is  the 
Ink  Spring,  the  water  of  which  is  alkaline  (table  3). 

SULPHUR  BANKS 

A  mile  down  stream  from  The  Geysers  is  another  fumarole  field, 
similar  in  character  to  that  just  described  and  of  much  greater  extent, 
known  as  the  Sulphur  Banks.  Its  barren  surface  steaming  slightly  in 
summer  and  marked  here  and  there  with  white  patches  of  salt  never 
fails  to  attract  attention  and  forms  a  conspicuous  landmark  for  those 
who  approach  The  Geysers  from  the  south  and  west.  Ground  tem¬ 
peratures  here  in  the  summer  of  1924  reached  98°  C.  not  far  from  the 
surface  in  a  number  of  places.  Furthermore,  the  aggregate  amount 
of  heat  escaping  from  the  whole  surface  may  be  considerable.  The 
ground  is  soft  and  frequently  more  or  less  muddy,  but  there  are  no 
springs  within  the  area  proper.  In  the  gulley  which  bounds  it  on  the 
east  there  are  a  few  hot  springs  of  which  the  Indian  Mud  Spring 
(table  3)  is  the  only  one  worthy  of  notice.  A  small  deposit  of  sulphur 
was  formerly  mined  at  the  Sulphur  Banks. 

Two  and  a  half  miles  from  The  Geysers,  up  Sulphur  Creek  at  the 
foot  of  a  ledge  of  schist  opposite  Foss’s  cabin,  a  little  hot  water  issues 
at  the  edge  of  the  creek.  Three-quarters  of  a  mile  north  from  this 
point  on  Little  Sulphur  Creek  there  is  a  bit  of  meadow  where  two 
springs  of  moderate  discharge  emerge.  The  hotter  spring  had  a  tem¬ 
perature  of  78°  C.  in  June  1925.  A  very  little  hot  water  issues  also  at 
other  points  along  the  creek.  Opposite  the  Fairchild  cabin  three  miles 
above  The  Geysers  Hotel  a  few  hot  springs  are  found  along  another 
little  run.  The  highest  temperature  there  was  71°.  Slight  bleaching 
of  the  ground  along  the  slope  indicates  former  fumarole  activity,  but 
very  little  gas  is  now  escaping,  and  doubtless  in  consequence  of  this 
the  ground  about  the  springs  is  covered  with  vegetation.  Both  locali¬ 
ties  are  thermally  insignificant. 

A  half  mile  upstream  from  the  last,  the  explorer  finds  another 
tributary  of  Sulphur  Creek  somewhat  larger  in  size.  Following  this 
little  stream  for  a  short  distance  he  comes  suddenly  out  of  the  dense 
bush  into  barren  ground  where  considerably  higher  temperatures  are 
found.  On  the  west  side  a  sloping  area  30  by  100  yards  in  extent  is 
dotted  with  insignificant  muddy  springs  where  temperatures  from 


95 


83°  to  95°  C.  were  observed.  On  the  opposite  side  of  the  creek  is  a 
short  line  of  diminutive  fumaroles,  several  of  which  reached  97°  in 
temperature.  The  altitude  here,  as  indicated  by  the  aneroid,  is  about 
1,800  feet.  Patches  of  bleached  ground  here  and  there  in  the  thicket 
beyond  show  that  fumarole  activity  was  at  one  time  more  extended 
than  it  is  today. 


LITTLE  GEYSERS 

Five  miles  up  from  The  Geysers  and  not  far  below  the  Socrates 
Quicksilver  Mine,  a  branch  from  the  northeast,  not  very  much  smaller 
than  the  main  stream,  flows  into  Sulphur  Creek.  Following  this 
branch  for  half  a  mile  one  enters  an  amphitheater  known  as  The 
Little  Geysers.  It  is  about  a  mile  in  diameter  surrounded  by  steep 
rocky  walls,  several  hundred  feet  in  height,  on  the  northeast,  north 
and  west,  but  falling  away  on  the  south  and,  especially  on  the  south¬ 
west.  The  stream  crosses  the  basin  from  north  to  south.  There  is 
hardly  any  timber  to  be  seen,  but  the  whole  area  except  a  few  acres 
in  the  central  portion  is  covered  with  a  dense  growth  of  stiff  thorny 
underbrush  which  hinders  exploration  considerably.  No  igneous  rocks 
have  been  found  here;  like  The  Geysers  area,  the  surface  is  covered 
with  serpentines,  sandstones,  more  or  less  altered,  schists  and  other 
metamorphics.  North  of  a  small  unoccupied  stone  cabin  about  the 
center  of  the  basin,  a  narrow  outcrop  of  mica  schist  runs  north  and 
south  for  some  hundreds  of  yards. 

Drainage  at  The  Little  Geysers  is  scant  in  the  summer  time.  The 
discharge  of  the  stream  at  a  point  250  yards  south  of  the  cabin  was 
estimated  from  rough  measurements  in  June  1925  at  300,000  gallons 
(about  1,000,000  kg.)  per  day,  and  in  June  1924  it  was  certainly  much 
less  than  that.  Neither  here  nor  elsewhere  in  this  basin  is  there  any 
indication  of  much  ground  water  at  any  time. 

Thermal  activity  is  now  practically  confined  to  a  few  acres  in  the 
central  portion  of  the  area,  but  elsewhere,  especially  to  the  southwest, 
the  observer  will  notice  at  intervals  small,  bare,  gleaming  white  areas 
like  oases  in  the  dense  bush,  which  on  examination  prove  to  be 
the  seat  of  old  fumarole  action.  The  rocks  are  in  various  stages  of 
alteration,  often  entirely  changed  to  opal  which  is  occasionally  asso¬ 
ciated  with  sulphur,  and  at  one  or  two  points  with  steam  and  hydrogen 
sulphide. 

All  the  hot  springs  are  grouped  within  a  few  hundred  yards  to  the 
east  and  south  of  the  cabin.  Directly  east  at  the  end  of  a  swale  about 
150  yards  in  length  steam  is  rising  among  the  rocks,  and  in  June  1925 
there  were  four  hot  muddy  springs,  two  of  which  reached  a  tempera¬ 
ture  of  96°  C.  A  larger  but  shallow  mud-spring,  much  nearer  the 
cabin  which  has  been  used  as  a  vapor  bath,  had  a  temperature  of  92°, 
and  there  were  several  pools,  somewhat  cooler,  close  by  it.  Seasonal 


96 


differences  were  most  noticeable  in  this  swale  where  in  June  1924 
hardly  any  water  was  visible. 

Fifty  yards  south  to  southwest  of  the  cabin  is  a  little  group  of  hot 
pools  containing  more  water  which  seems  to  be  chiefly  supplied  by 
the  scant  drainage  from  the  above-mentioned  swale.  In  June  1925 
the  hottest  of  these  showed  a  temperature  of  81°  C.  More  gas  was 
observed  escaping  from  these  pools  than  anywhere  else  at  The  Little 
Geysers  (fig.  31).  In  late  June  1926  when  gases  were  collected  at  The 
Little  Geysers  the  hottest  spring  in  the  area  southwest  of  the  cabin 
had  a  temperature  of  95.9°  (No.  5).  The  temperature  in  Spring  4, 
10  feet  from  the  last,  was  71°. 


Fig.  31 — Spring  at  The  Little  Geysers,  southwest  of  cabin.  (Gas  sample 
No.  4,  table  9,  was  collected  from  this  spring.) 


On  a  small  barren  flat  just  south  of  the  pools,  and  at  a  little  higher 
level,  there  is  another  group  of  very  small  hot  muddy  springs  and  one 
or  two  mud  pots  where  the  maximum  temperature  in  1925  was  95.5°  C. 
(fig.  32).  In  the  drier  season  of  1924  temperatures  as  high  as  97°  C. 
were  observed.  The  altitude  here  is  estimated  by  the  aneroid  at 
2,300  feet  at  which  the  boiling  point  of  water  varies  around  97.5°  C. 

Except  for  insignificant  amounts  of  serpentine  on  the  south  side 
of  the  flat  (very  possibly  boulders)  the  rocks  are  completely  decom¬ 
posed  to  silica  and  oxide  of  iron.  Chemical  activity  now  in  progress 
here  is  evidently  very  slight.  The  waters  analyzed  (table  3)  show 


97 


very  little  acid;  they  are  on  the  verge  of  neutrality  and  the  small 
amount  of  sulphate  they  contain  indicates  that  they  have  never 
possessed  much  acid  at  any  stage  of  their  history.  This  accounts  for 
the  precipitation  of  oxide  of  iron,  a  process  that  is  no  doubt  cumu¬ 
lative.  None  of  the  black  sulphide  of  iron  often  noticed  at  The 
Geysers  has  been  found  in  any  of  these  springs.  The  supply  of 
sulphur  is  evidently  very  limited,  for  the  total  amount  of  gas  escaping 
is  small  and  the  percentage  of  hydrogen  sulphide  it  contains  is  very 
slight;  in  fact  the  gases  collected  here  in  1926  showed  not  a  trace  of 
it  (table  9). 


Fig.  32 — One  of  small  hot  springs  at  The  Little  Geysers,  Central  Plateau. 
(Gas  sample  No.  3  was  collected  from  this  spring.) 


Most  of  the  springs  described  have  little  or  no  overflow.  What 
there  is  either  evaporates  or  finds  its  way  into  the  stream  by  sub¬ 
surface  channels.  But  in  estimating  the  total  discharge  of  hot  water 
from  the  basin  it  must  not  be  overlooked  that  there  is  a  certain 
amount  of  seepage  along  the  creek,  though  only  one  distinct  spring 
vent  was  discovered.  The  Chicken  Soup  Spring,  on  the  eastern  side 
of  the  stream  several  hundred  yards  south  of  the  cabin,  discharges 
more  water  than  any  other  spring  at  The  Little  Geysers.  Its  tem¬ 
perature  in  June  1925  was  only  71°  C.  From  most  of  the  area  under 
discussion  the  heat  loss  also  must  be  very  slight.  The  heat  carried 
away  by  the  stream,  however,  is  not  entirely  negligible  and  may  be 
indicative  of  a  considerable  supply  of  subterranean  steam.  In  June 
1924  the  water  where  the  stream  narrows  below  the  Chicken  Soup 
Spring  had  a  temperature  of  about  50°  C.  At  that  time  circum¬ 
stances  prevented  an  estimate  of  the  stream  discharge.  In  June  1925 


98 


the  temperature  in  the  same  place  and  for  some  distance  below  was 
26°  C.,  which  is  10°  higher  than  it  was  above  the  hot  area.  Estimating 
the  discharge  at  1,000,000  kilograms  a  day  the  total  subterranean  heat 
carried  away  every  24  hours  by  this  little  brook  would  amount  to 
10,000,000  kilogram  calories. 

In  brief  The  Little  Geysers  may  be  characterized  as  a  basin  of 
limited  drainage  where  the  hot  springs  are  correspondingly  small,  a 
relation  confirming  the  view  already  expressed  concerning  the  role  of 
ground  water  in  hot  springs. 


CALISTOGA 

The  town  of  Calistoga  lies  at  the  head  of  the  Napa  Valley  not  far 
from  the  base  of  Mount  St.  Helena,  Its  altitude  is  much  lower  than 
that  of  the  other  localities  described  and  the  manifestation  of  its 
thermal  energy  is  different,  but  because  it  is  aligned  with  these  other 
localities,  and  because  thermal  localities  so  related., §eem  to  be  vitally 
connected  through  the  agency  of  faults,  a  brief  account  of  the  thermal 
activity  at  Calistoga  may  properly  find  a  place  here. 

Until  recent  years  there  was  a  small  group  of  hot  springs  near  a 
knoll  of  tuff  at  the  eastern  edge  of  the  town.  Waring,1  who  gives  a 
description  of  the  springs  and  their  environs,  says  that  in  1910  the 
principal  spring  discharged  about  a  gallon  of  water  per  minute  and 
had  a  temperature  of  173°  F.  (about  78°  C.).  The  analysis  of  the 
waters  which  he  cites  shows  that  they  are  alkaline  waters  of  low  con¬ 
centration,  the  chief  acid  radicals  being  C03,  Cl  and  S04,  while  sodium 
is  the  most  important  metal.  Small  mounds  of  characteristic  siliceous 
sinter,  doubtless  deposited  by  the  waters,  were  found  here  in  1924  by 
one  of  the  authors.  It  has  already  been  incidentally  stated  that  the 
flow  of  these  springs  ceased  when,  a  few  years  ago,  a  number  of  wells 
were  drilled  in  the  vicinity  for  the  purpose  of  developing  a  water 
supply.  The  result  of  the  undertaking  was  as  remarkable  as  it  was 
unexpected.  Instead  of  the  cold  water  they  sought  the  promoters 
found  it  boiling  hot  and  associated  with  steam  of  such  pressure  that 
the  water  gushed  out  in  the  form  of  geysers  (fig.  33).  That  these 
geysers  are  true  periodic  springs  there  can  be  no  question.  In  June 
1924  two  of  them  were  seen  in  action  by  one  of  the  authors.  The 
first,  near  Pacheteau’s  baths,  threw  out  a  jet  of  water  quite  regularly, 
about  once  a  minute,  the  eruption  lasting  for  a  fraction  of  a  minute 
and  then  subsiding  completely.  The  water  column,  which  was  about 
the  size  of  the  jet  from  a  large  hose,  rose  to  the  height  of  75  or  100 
feet  and  resembled  a  true  geyser  in  all  the  details  of  its  behavior. 
The  other,  a  geyser  of  about  the  same  magnitude,  was  also  seen  in 
action.  It  was  said  to  erupt  about  once  in  35  minutes.  According 
to  A.  Rocca  of  Calistoga,  who  kindly  supplied  us  with  the  information, 

1  Op.  cit.,  p.  108. 


99 


thirteen  geyser  wells  have  been  drilled  at  Calistoga  and  Myrtledale, 
all  but  three  of  which  are  now  capped  so  that  the  hot  water  can  be 
utilized. 

It  is  not  proposed  on  the  basis  of  a  few  superficial  observations  to 
attempt  a  detailed  explanation  of  this  remarkable  phenomenon,  but 
there  are  certain  relations  to  the  subject  as  a  whole  which  ought  to  be 
pointed  out.  The  waters  are  typical  geyser  waters  in  their  compo¬ 
sition  and,  like  the  other  alkaline  waters  of  the  St.  Helena  Range, 


Fig.  33 — Artificial  geysers  at  Calistoga,  California,  developed  unexpectedly  by 

drilling.  Photo  by  J.  D.  Grant. 


contain  a  certain  amount  of  sulphate.  Whether  this  sulphate  is 
related  to  their  chemical  history  in  the  same  way  as  it  is  in  the  alka¬ 
line  waters  we  have  investigated,  and  whether  the  chloride  which  is 
comparatively  high  in  the  Calistoga  waters  is  of  magmatic  origin  or 
is  directly  derived  from  marine  sediments,  are  questions  which  we 
raise  without  answering. 

On  the  other  hand,  the  fault  which  according  to  Waring  has  been 
traced  in  this  part  of  the  valley,  may  very  well  be  directly  related  to 
The  Geysers  canyon,  which  appears  to  be  a  fault  valley,  and  though 
the  chemical  processes  in  progress  here  may  or  may  not  closely 
resemble  those  at  The  Geysers,  such  processes,  as  we  have  pointed 


100 


out,  are  probably  of  a  rather  superficial  character  depending  on  the 
nature  of  the  surface  rock  and  certain  other  conditions  which  vary 
locally;  the  vital  cause  of  the  phenomena  which  have  been  disclosed 
by  drilling  seems  to  be  identical  in  both  cases,  namely  a  supply  of 
subterranean  steam.  The  differences  in  behavior  shown  by  the  wells 
of  Calistoga  seem  to  be  a  natural  result  of  the  larger  water  supply  in 
this  broader  and  better-watered  valley,  and  perhaps  also  the  result  of 
a  steam  supply  of  smaller  volume  and  pressure. 

COMPARISON  OF  THE  GEYSERS  CANYON,  CALIFORNIA,  WITH  THE 

FUMAROLE  FIELDS  OF  TUSCANY 

To  those  who  are  interested  in  ultimate  causes  as  well  as  to  those 
whose  interest  centers  in  a  novel  industrial  project  which  may  eventu¬ 
ally  reach  great  importance,  a  brief  comparison  of  the  main  features 
of  the  thermal  activity  in  Tuscany  with  those  in  The  Geysers  canyon 
may  be  welcome.1 

Thermal  activity  in  Tuscany  is  confined  to  that  portion  of  the 
Catena  Metallifera,  a  mountain  range  running  parallel  to  the  west 
coast  of  Italy,  which  is  hemmed  in  between  the  higher  valleys  of  the 
Cecina  and  Cornia  Rivers  [Ginori  Conti  (a),  p.  4].  Both  hot  springs 
and  fumaroles,  “lagoni”  and  “soffioni,”  are  numerous  over  an  area  of 
approximately  100  square  miles,  but  the  latter  on  account  of  their 
spectacular  nature  as  well  as  their  economic  significance  have  prac¬ 
tically  monopolized  the  attention  of  most  observers.  Industrial 
development,  which  has  been  in  progress  here  for  the  last  three- 
quarters  of  a  century,  has  considerably  altered  the  natural  surface  of 
the  country  and  has  given  rise  to  artificial  pools  and  steam- wells,  but 
whether  artificial  or  natural  the  terms  “lagoni”  and  “soffioni”  are 
applied  indiscriminately,  with  a  result  somewhat  confusing  to  the 
reader.  Nevertheless  it  seems  clear  from  the  accounts  of  early  ob¬ 
servers  and  the  evident  impression  left  on  their  minds  that  the  natural 
thermal  activity  in  the  Tuscan  fumarole  fields2  is  far  more  intense 
than  that  manifested  in  The  Geysers  canyon  which  we  have  been 
considering.  According  to  De  Stefani,  in  Tuscany  the  fumaroles 
issue  from  sediments — sandstones,  flints,  limestones  and  marls  of 
eocene  and  miocene  age  associated  with  serpentine,  schists  and  gabbro. 
That  the  hot  springs  and  fumaroles  follow  “lines  of  fracture”  (faults) 
was  clearly  brought  out  75  years  ago  by  Murchison3  and  later  con- 

1  The  data  on  the  Tuscan  locality  are  derived  mainly  from  the  following  publications: 

De  Stefani,  I  soffioni  boraciferi  della  Toscana.  Memorie  della  Society  geografica  Italiana 

VI,  2,  410,  1897. 

Nasini,  I  soffioni  boraciferi  e  la  industria  dell’  acido  borico  in  Toscana,  Roma,  1907.  (This 
work  includes  a  bibliography.) 

Ginori  Conti,  (a)  The  natural  steam  power-plant  of  Larderello,  Firenze,  1924:  ( b )  Sur  l’utiliza  - 
tion  industrielle  des  manifestations  thermiques  terrestres,  Chimie  et  Industrie  Paris. 

2  Hamilton,  Quarterly  Journal  of  Geology,  1,  273,  1845. 

3  Quar.  Jour.  Geol.,  6,  367,  1850. 


101 


firmed  in  detail  by  De  Stefani.  Many  facts  indicate  that  the  store  of 
ground  water  is  considerable;  the  hot-spring  pools  are  comparatively 
large,  water  is  often  encountered  in  drilling  and  true  geysers  are 
mentioned  by  De  Stefani  as  occurring  at  Serazzano  and  Monte- 
rotondo.1  The  statement  of  Ginori  Conti  that  the  springs  and  fuma- 
roles  occur  in  “absolutely  barren  ground”  would  indicate  acid  decom¬ 
position  of  the  rocks  and  this  has  been  made  clear  by  the  extensive 
observations  which  De  Stefani  has  recorded.  The  alteration  products 
are  silica  and  various  sulphates,  including  large  amounts  of  calcium 
sulphate  and  several  borates  which  are  apparently  much  smaller  in 
amount. 


STEAM-WELLS 

Temperatures  in  the  Tuscan  fields  are  reported  to  vary  from  100 
to  190°  C.  [Nasini,  op.  cit.,  pp.  91-92].  The  more  recent  statements 
of  Ginori  Conti  have  not  extended  the  range. 

How  far  these  temperatures  apply  to  natural  fumaroles  is  not 
clear,  but  the  highest  temperatures  appear  to  have  been  obtained  in 
the  wells.  The  boring  of  small  and  shallow  wells  has  long  been 
resorted  to  in  the  preparation  of  boric  acid,  the  steam  being  used  in 
the  evaporation  of  the  solutions.  The  drilling  of  larger  and  deeper 
wells  for  steam  power  has  been  in  progress  only  about  20  years.  The 
depth  of  these  modern  wells  varies  from  60  to  200  meters  [Ginori 
Conti  (a),  p.  11]. 

Pressure  in  different  wells  varies  greatly  with  locality  and  with 
depth,  though  no  simple  relation  to  the  latter  has  been  discovered. 
In  the  older  and  smaller  wells  pressures  may  be  as  low  as  1.5  or  1.75 
atmospheres  [Nasini,  op.  cit.,  p.  93]  and  in  the  earlier  borings  of  the 
present  period  it  never  reached  above  5  atmospheres,  but  in  a  recent 
well  at  Serazzano  of  90  meters  depth  a  pressure  of  7  atmospheres  was 
attained  with  the  valve  still  partially  open  [Ginori  Conti  (a),  p.  16]. 
In  a  deep  well,  still  more  recently  developed,  the  pressure  though  not 
directly  measured  has  been  estimated  from  quantitative  data  at  14 
atmospheres  (about  200  pounds  per  square  inch)  [Ginori  Conti  (6), 
p.  6].  As  a  matter  of  prudence  the  most  powerful  wells  in  Tuscany 
are  apparently  never  completely  closed.  The  temperature  and  pres¬ 
sure  measurements  of  Nasini  on  the  sofhoni  have  already  been  re¬ 
counted  (p.  63)  and  it  will  be  recalled  that  they  proved  the  important 
fact  that  the  steam  here  is  superheated.  The  measurements  seem  to 
have  been  made  not  in  the  natural  fumaroles  but  in  the  older  shallow 
wells.  Nasini’s  statement  has  since  been  confirmed  by  Ginori  Conti 
on  the  basis  of  further  data  from  the  deeper  wells. 

1  Ginori  Conti  informs  us  that  these  have  now  disappeared  as  a  result  of  drilling. 


102 


STEAM  OUTPUT 

Till  recent  years  the  greatest  output  of  steam  was  from  a  rather 
small,  shallow  well  at  Larderello,  known  as  “Forte”  which  yields  4,000 
kilograms  (8,800  pounds)  of  steam  per  hour  at  a  pressure  of  about 
one  atmosphere  effective  [Ginori  Conti  (a),  p.  9].  The  powerful 
well  at  Serazzano,  just  referred  to,  delivers  24,000  kilograms  (52,800 
pounds)  per  hour  at  a  pressure  of  one  atmosphere  effective  and  13,000 
kilograms  (28,600  pounds)  per  hour  5  atmospheres  effective.  It  is 
an  interesting  fact  that  with  increasing  pressure  the  output  of  the 
more  powerful  wells  is  much  less  affected  than  that  of  the  weaker 
ones.  A  very  powerful  well  at  Castelnuovo  has  yielded  60,000  kilo¬ 
grams  (132,000  pounds)  of  steam  per  hour  at  a  pressure  of  one 
atmosphere  effective  and  over  15,000  kilograms  (33,000  pounds)  at 
two  atmospheres  effective  [Ginori  Conti  (a),  p.  16]. 

About  1923,  12  wells  at  Larderello  yielded  120,000  kilograms  of 
steam  per  hour  at  two  atmospheres  absolute  pressure  or  10,000  kilo¬ 
grams  (22,000  pounds)  per  well  on  the  average  [Ginori  Conti  (a), 
p.  13]  as  compared  to  an  average  of  about  34,000  pounds  at  a  pressure 
of  about  five  atmospheres  effective  from  four  wells  at  The  Geysers. 
The  present  output  at  Larderello  alone  is  given  as  190,000  kilograms 
of  steam  per  hour  [Ginori  Conti  ( b ),  p.  9],  while  an  interesting  calcu¬ 
lation  based  on  the  total  production  of  boric  acid  and  the  known  rela¬ 
tion  of  it  to  the  amount  of  steam  brings  the  total  amount  of  steam 
now  available  in  all  the  fumarole  areas  up  to  several  million  kilograms 
per  day  [Ginori  Conti  (b),  p.  11]. 

The  origin  of  this  steam  is  regarded  by  De  Stefani  as  deep-seated. 
His  conclusion  has  a  special  interest  because  the  evidence  on  which 
it  rests  is  of  quite  a  different  character  from  that  advanced  by  the 
authors  of  this  paper  for  the  origin  of  the  steam  in  The  Geysers 
canyon.  De  Stefani’s  most  convincing  argument  is  that  the  boric  acid 
which  invariably  accompanies  the  steam  is  never  found  (except  as 
an  alteration  product)  in  the  superficial  strata;  a  source  of  it  has  not 
been  discovered  above  the  horizon  of  the  most  ancient  granites.  The 
high  temperature  of  the  steam  and  the  constant  percentage  of  gases 
are  also  regarded  by  him  as  evidence  of  the  deep-seated  origin  of  the 
steam. 

GASES 

Here  as  elsewhere  in  fumarole  regions  volcanic  gases  are  prevalent. 
Their  composition  has  been  the  subject  of  many  chemical  investiga¬ 
tions.  Nasini  (op.  cit.,  p.  93),  whose  work  appears  to  be  the  most 
reliable,  gives  the  following  analyses  of  gases  from  two  different 
fumaroles  at  Larderello. 

Nasini  states  that  the  natural  gas  in  the  vapor  amounts  to  2  per 
cent  to  3  per  cent  by  volume  (3  per  cent  to  5  per  cent  by  weight). 


103 


Ginori  Conti  (b,  p.  11)  finds  little  connection  between  the  thermal 
phenomena  and  the  superficial  strata  in  which  the  fumaroles  issue; 
only  in  the  percentage  of  the  non-condensable  gases  does  there  appear 
to  be  any  relation.  The  gases  vary  from  2  per  cent  to  over  6  per  cent 
by  weight  and  the  amount  is  said  to  be  constant  along  the  same  fault 
line  ( b ,  p.  11 ). 


In  100  parts  of 
natural  gas 

Gas  in  soffione 
Casotto 

Gas  in  soffione 
Tini 

H2S . 

2.070 

2 . 000 

CO> . 

92.800 

92.000 

CH, . 

1.400 

1 . 900 

h2 . 

2.600 

2 . 400 

o2. . 

.050 

.200 

n2 . 

1.048 

1.455 

A . 

.021 

.029 

He . 

.010 

.014 

For  further  details  on  geology,  power  installation,  etc.,  the  student 
of  the  subject  should  consult  the  original  papers. 

From  this  brief  comparison  of  the  two  areas  in  Italy  and  Cali¬ 
fornia  many  points  of  similarity  in  geologic  conditions  are  seen, 
though  the  Tuscan  area  is  much  more  extensive  and  the  intensity  of 
thermal  activity  in  undisturbed  ground  appears  to  be  much  greater. 
The  principal  chemical  changes  in  progress  near  the  surface  of  the 
ground  seem  to  be  of  the  same  general  character,  the  differences  being 
due  more  to  the  nature  of  the  superficial  rock  than  to  differences  in 
the  composition  of  the  gases.  The  total  amount  of  the  alteration  in 
Tuscany  also  appears  to  be  much  greater,  probably  on  account  of  the 
greater  quantity  of  vapors  constantly  escaping  there  and  to  the 
peculiarly  susceptible  nature  of  limestone. 

The  total  amount  of  non-condensable  gas  is  somewhat  greater  in 
Tuscany  than  in  California,  and  so  far  as  there  is  such  a  difference  the 
steam  from  the  latter  has  the  advantage  in  the  generation  of  power 
by  the  ordinary  steam  turbine.  It  should  be  remembered,  however, 
that  the  difference  is  exaggerated  when  percentages  are  stated  by 
weight  for  the  Tuscan  gas  is  denser  and  it  is  volume  which  really 
counts. 

In  composition  the  gases  in  the  two  localities  differ  considerably 
from  one  another.  Carbon  dioxide  is  the  predominant  constituent  of 
each,  but  the  percentage  of  it  is  much  higher  in  Tuscany.  Hydrogen 
sulphide,  chemically  the  most  active  of  the  gases,  is  somewhat  greater 
in  amount  in  the  California  wells  though  still  of  the  same  order  of 
magnitude.  The  California  gases  are  much  higher  also  in  hydrogen 
and  methane  but  the  significance  of  the  fact  is  not  yet  apparent. 


104 


When  we  come  to  a  comparison  of  the  steam-wells  in  the  two 
localities,  one  of  the  most  important  facts  to  be  stressed  is  the  super¬ 
heated  character  of  the  original  steam  in  both.  It  must  be  borne  in 
mind  that  only  a  few  wells  in  California  have  yet  been  developed,  but 
the  maximum  temperature  is  as  high  as  it  is  in  Tuscany,  and  half  the 
wells  are  superior  both  in  pressure  and  in  steam  output  to  any  yet 
reported  from  Italy. 

SUMMARY 

The  region  studied  in  this  paper  includes  small  areas  of  the  Coast 
Range  in  California,  specifically  in  the  St.  Helena  Range.  The  slopes 
of  this  range  are  generally  covered  with  sediments  and  metamorphics 
but  exposures  of  andesite  on  the  high  peaks,  the  occurrence  of  small 
areas  of  lava,  tuff  and  obsidian  at  certain  other  points  and  the  dis¬ 
covery  by  drilling  of  gabbro  at  a  depth  of  230  feet  at  The  Geysers,  all 
proclaim  this  a  volcanic  region.  Another  fact  of  considerable  im¬ 
portance  in  support  of  the  conclusions  reached  concerning  the  thermal 
activity  in  this  region  is  that  there  is  evidence  of  a  fault  extending 
along  the  west  side  of  the  range  for  a  distance  of  about  25  miles. 

Observations  on  the  hot  springs  of  this  locality  not  only  confirm  the 
conclusions  reached  in  the  course  of  investigations  in  the  Lassen 
National  Park  in  nearly  every  particular,  but  materially  extend  our 
knowledge  in  several  directions. 

(1)  Of  first  importance  are  the  observations  and  tests  that  concern 
the  great  store  of  hot  steam,  increasing  with  depth,  which  drilling 
proves  may  be  tapped  at  The  Geysers  not  far  below  ground  in  the 
hot  area  anywhere,  even  in  spots  where  formerly  there  was  no  indi¬ 
cation  of  abnormal  temperature.  That  similar  supplies  of  subter¬ 
ranean  volcanic  steam  of  industrial  importance  may  be  developed  in 
many  other  fumarole  districts,  as  Prince  Ginori  Conti  believes,  is 
highly  probable,  and  that  they  are  the  secret  of  the  immense  stores 
of  heat  and  its  ready  transmission  in  the  great  geyser  basins  seems 
beyond  doubt.  The  fact  that  the  steam  at  The  Geysers  rises  in  a 
region  where  all  signs  point  to  a  meager  supply  of  ground  water,  that 
it  is  accompanied  by  volcanic  gases,  and,  almost  equally  significant, 
that  the  steam  is  superheated  like  the  steam  at  Larderello  and  like 
that  in  many  fumaroles  at  Katmai  and  probably  elsewhere,  points 
to  a  magmatic  origin.  The  eventual  saturation  of  the  steam  in  the 
wells  at  the  Geysers  is  shown  by  tests  to  be  a  subsequent  development 
which  requires  appreciable  time  and  probably  occurs  in  the  wells 
themselves. 

(2)  While  the  volcanic  gases,  hydrogen  sulphide,  or  to  be  more 
accurate  its  oxidation  product  sulphuric  acid,  and  to  a  lesser  degree 
carbonic  acid,  are  the  active  agents  in  rock  decomposition,  the  actual 
process  appears  to  be  confined  to  a  zone  near  the  surface.  This  is 


105 


shown  by  the  direct  relation  between  the  composition  of  the  spring- 
waters  and  the  superficial  rocks,  the  most  important  of  which  is  ser¬ 
pentine;  by  the  seasonal  variation  in  the  discharge  of  a  large  number 
of  the  springs  which  is  measurable;  by  the  mutual  relation  between 
springs  and  fumaroles  expressed  in  the  appearance  of  hot  springs  at 
new  points  in  wet  weather  and  the  drying  up  of  certain  hot  springs 
with  advancing  summer,  and  also  by  the  evidence  revealed  in  drilling. 

(3)  Much  additional  information  has  been  collected  on  the  causes 
of  acid  and  alkaline  springs  and  on  their  relation  to  each  other.  A 
marked  difference  in  concentration  between  the  two  classes  which  was 
forecast  from  incomplete  evidence  in  the  Lassen  National  Park  is 
here  fully  borne  out — the  concentration  of  the  acid  springs  being  so 
much  higher  as  a  rule  as  to  constitute  a  different  order  of  magnitude. 
It  has  been  possible  to  trace  many  springs  pretty  definitely  to  the 
ground  where  they  rise  and  to  connect  the  acid  springs  with  places 
where  oxidation  is  active,  and  the  alkaline  springs  with  places  where 
oxidation  is  feeble.  There  is  nothing  to  show  that  the  acid  waters 
were  formerly  alkaline,  as  some  suppose,  and  while  the  evidence  indi¬ 
cating  that  the  alkaline  springs  were  acid  in  their  beginning  may  not 
be  completely  convincing  to  all,  it  is  quite  in  accord  with  the  facts  so 
far  as  they  are  known. 


Fig.  34 — The  Geysers,  early  morning.  1925. 

(4)  A  comparison  of  the  thermal  activity  in  the  St.  Helena  range 
with  that  of  Tuscany,  so  far  as  the  latter  can  be  determined  from  the 
literature,  has  been  made. 


106 


ACKNOWLEDGMENT 

The  authors  wish  to  express  their  thanks  for  the  cordial  cooperation 
they  received  at  “The  Geysers"  at  every  stage  of  the  work.  They  are 
under  obligations  to  many  people,  particularly  to  J.  D.  Grant,  presi¬ 
dent  of  the  development  company,  and  to  J.  D.  Galloway,  the  engi¬ 
neer;  to  the  employees  of  the  Diamond  Drill  Contracting  Company, 
especially  to  Mr.  Butler;  to  R.  B.  Kidd  for  services  of  many  kinds 
and  to  Bob  Senteney  for  assistance  in  the  field. 


Geophysical  Laboratory , 

Carnegie  Institution  of  Washington , 
December,  1926. 


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